How strong was Start of Series Sailor Moon

 

This is something I was talking about recently with some other Sailor Moon scalers. I am very interested in comparing characters at various stages of their progression. I was considering my favorite character and wondering alright if she was as was at the start of her development, who can clear this very first benchmark of hers?" In other words, what characters even if they lose to Sailor Moon are strong to begin the comparison.

If you're reading this blog this is probably not the first time you're reading about Sailor Moon, but in case you're unaware Sailor Moon is actually an extremely powerful character, much stronger then most characters that one would expect. For reference the most common matchups people put her against are characters like Goku, Pegasus Seiya, Cardcaptor Sakura, Kami Madoka, Supergirl etc. So how strong was she at the start of her progression? The first time Sailor Moon gets more powerful is Act 4, so this should include all feats from the first three acts which form their own sub arc, the Jadeite arc. 

By far the biggest explicit feat this Sailor Moon has is that her ultrasonic waves would threaten Jadeite's world in Act 3. This is substantiated when Sailor Mars' first attack accidentally destroys the same dimension later that chapter as a side effect. This dimension's size is contested but there is a very clear moon within the dimension, with the destruction of a planet-moon system like ours requiring large planet bordering on low stellar power. This is consistent with the Parallel Senshi, Five Child Senshi from a parallel dimension stopping a planetary threat seconds after their first transformation into Sailor Senshi. 

There is argument for them to be in the stellar range in general. The Ultrasonic Crying is considered a joke attack and borders on this level accidentally. The Stars are living entities in the Sailor Moon universe and yet are under the protection of the Sailor Senshi suggesting the Senshi can battle entities that would threaten such. Sailor Moon Crystal which was directly overseen by Naoko Takeuchi the original author, suggests that the early First Arc Sailor Senshi are not that much weaker then the Late First Arc Senshi with the Heavenly Kings battling the Sailor Senshi fairly evenly early and late in the arc. This would suggest Sailor Moon would scale to a portion of the power the Late First Arc Senshi show destroying Kunzite's barrier that withstood energy comparable to a supernova, and above second arc fodder that can withstand being on a black hole. That the Early First Arc characters aren't THAT much weaker then the Late First Arc is also implied by Pre-Serenity Moon withstanding an attack from Kunzite, who Beryl considered still a threat to the Princess Serenity that tanked the prior supernova energy. 

Some argue the characters are weaker based on the sense that they don't seem to be cosmically strong at this point in the story with how the Senshi are shocked at the Silver Crystal's ability to easily destroy celestial bodies, or how Kunzite saying he would return the Senshi's attacks times 100 only threatens to destroy Tokyo. These arguments will often try to suggest the Moon in Jadeite's dimension is merely a visual effect and often try and tie it to Usagi's transformation. I rarely say this in fictional media analysis but the last point is just objectively wrong. The Moon is not caused by Usagi's transformation effect and to claim such requires one to essentially not be reading what happens as events happen in the manga between Usagi's transformation and Usagi's pre-battle speech where the Moon is seen including Ami teleporting in, the two finding Rei and Jadeite, and Jadeite taking Rei hostage. You can say it's inconsistent if you want and it very well may be, but trying to say the Moon is a transformation visual is objectively wrong. There are also arguments it should be much higher, usually the dashes of white on the page as indication of stars in Jadeite's dimension, using the fact that Stars are capable of "flooding the Milky Way", the belief Jadeite's dimension should be considered an entire universe, or the belief that the Senshi's power can affect higher dimensional ghosts. Each of these I don't really agree with either, though for different reasons. I bring both of these up only to say I recognize that there are other ways one can scale this, and I do not agree with much lower or much higher interpretations. 

In terms of speed Sailor Moon even at the start of her series gets the benefit comes from the fact that any entity of any power in this verse including entire alien species demonstrating the ability to traverse interstellar distances, much like other series with eldritch horror influences. Inhabitants from the worlds of Mau and Coronis came from distant star systems to Earth. The timeframe is unknown but the fact that these are biological entities who need such things as food and sleep puts an upper limit that requires speeds dozens to thousands of times the speed of light. The Ancient Moon People came to the Sol System from the "far galactic reaches" similarly with the people of Earth warring with and killing them. The Stars are living entities and a pair of them dozens of lightyears away come to Earth in humanoid form every year, requiring speeds dozens to thousands of times the speed of light. Minako even prior to her first transformation accidentally sends herself to Venus quickly with Light taking over 2 minutes to go the same distance, usually calced at somewhere between single digit FTL to triple digit FTL. All this suggests Sailor Moon while not at the extreme speeds she would get to later, should be likely hundreds or even thousands of times the speed of light. 

Even at the start of the series, though she doesn't know it, Usagi is a Sailor Senshi, an Avatar of a God, a Destined Soldier, Chosen by Fate. This gives her abilities. Even before awakening she was born with her guardian planet, the Moon, giving her protection from many haxes. For example for of the kinds of things the Sailor Senshi early in the story withstand, a Dark Agency villainess named LinLin brainwashed all of China and yet Minako was unaffected and Zoisite was able to drain energy from the entire town yet Usagi was able to withstand it without even transforming. As a Sailor Senshi, if Usagi dies she will reincarnate and reawaken eventually to her true identity, this Sailor Senshi self treated as her true self and mortal lifetimes as temporary disguises.

Even among this group Usagi is special though for her Sailor Crystal is the legendary Silver Crystal, supreme light of the universe and while it lays dormant within her early in the story, even dormant it can grant greater protection. When her Senshi powers were neutralized from Planet Nemesis, Usagi recovered quickly from the Paralysis of the Evil Eye technique, credited to the Silver Crystal. Also when Chibiusa was in distress, despite not have yet awakened the Silver Crystal within her, much like early Usagi, she was able to accidentally wander to Wiseman's domain outside space and time, "at the end of the world." This is because the Silver Crystal reacts to one's heart, and commands space and time. Should Beginning of Series Sailor Moon's heart be so distraught, a similar effect would presumably happen. 

The Silver Crystal is shown several times to react by itself to protect Usagi, growing into a barrier around her, creating an energy around her to protect her, or teleporting her outside of danger. This may apply even to beginning of series Sailor Moon.

All Sailor Senshi have an aura of stellar energy which can be utilized for "Henshin", transforming into their Sailor State. Doing such creates a blinding flash of light as well as a burst of energy that can be used for destruction. It is a holy energy, and stated to be their holiest power. It has been shown to allow for teleportation of oneself or others through dimensions, though at this point Usagi is unaware of such, and undoes spells that are negatively affecting a Senshi as shown when simply transforming reversed Palla Palla's spell switching Usagi and Chibiusa's ages. 

Their stellar energy has also been shown to do much more such as creating levitating energy bubbles around them, shooting generic energy blasts that seems to deconstruct enemies, and enchanting material objects to create new attacks themed around said attacks. Though it's unlikely Usagi at this point knows she can do any of that. 

While she doesn't have the cosmic senses she would have later, Sailor Moon would get enhanced senses immediately upon transforming for the first time, including her hairpieces hearing Naru's distant cries, and her goggles clairvoyantly showing her such. The Sailor Senshi regularly demonstrate the ability to see and interact with metaphysical entities including spirits, dreams, and even conceptual objects. They also possess enhanced psychic sensitivity and are shown numerous times to have prophetic dreams. 

Sailor Moon in Act 1 demonstrates two attacks. The first is more of a joke though, as when Usagi becomes upset enough and cries her hairpieces amplifies the crying into ultrasonic waves. This a sonic attack that created a sense of numbness and threatened to destabilize Jadeite's world should Usagi cry in that dimension, suggesting it can damage the fabric of space itself. This seems consistent with the way it was shown to be able to harm incorporeal ghosts in Chibiusa's Picture Diary 3. 

Sailor Moon's first real attack is the Moon Tiara Boomerang where she throws her tiara like a boomerang which cuts enemies and turns them to dust. She also shows hair ornaments she can use like darts in Act 2 though in Act 1 she presumably doesn't know she can do that yet. 

Finally it is noted that Sailor Senshi transform into women of strength and beauty, a woman among women. This supernatural beauty gives the Sailor Senshi a level of social influencing that can cause enemies to act sub-optimal against them. For instance when the Terrorist Warlord Demande saw Usagi's future self, he immediately fell in love with her and dedicated himself to capturing her instead of killing her. 

Obviously the weakness this Usagi would have is she has yet to even begin developing as a Sailor Senshi. As she was Princess Serenity in her last life, she is the only one of the Inner Senshi to have had no combat experience in either lifetime, and lacks the skill or fortitude of a soldier. She hasn't yet developed as a person and is still clumsy, a crybaby, and cowardly, though of course she does still have her biggest strength which is her love that lets her overcome her weaknesses to become a hero should people need her. 

So that is Start of Series Sailor Moon, the benchmark to even begin comparing to Sailor Moon powerscaling-wise. She has Large Planet to Stellar Level Power, FTL+ Speed, Two Different Attacks including one that has an offensive hax (turning to dust) and the other of which negates a common defensive hax (intangibility), hax resistances to a large variety of haxes (including at least mind manipulation, energy manipulation, age manipulation, poison, and paralysis), possibly other potent defensive options, enhanced senses, social influencing, and powerful spacetime manipulation if her heart becomes chaotic enough. There's few protagonists who could beat her at the start of their own series, unless they're one of those protagonists that don't get any stronger and just start at extremely powerful. 

How does she compare to my other favorite series protagonists (beginning of series):

Of the 32 other series on my favorites list I think 22 there isn't really any good argument for them being able to beat even Start of Series Sailor Moon. Some of them have things that might be relevant, the Cutie Honey Flash version of Cutie Honey can reach similar attack potency but is vastly slower and would just blitzed. Luz from the Owl House and Samus from Metroid might have rivaling or even superior speeds depending on your interpretations but have nowhere near the same level of power. Yusuke from Yu Yu Hakusho is a ghost at the start of the series but the Ultrasonic Crying can hit ghosts. There are only 10 that could or maybe could defeat Start of Series Sailor Moon at their respective start of series, five of which I think are arguable and five of which I feel more confident in. The five I think are questionable:

Cures: My favorite Pretty Cure Seasons are Heartcatch, DokiDoki, and Go Princess but Cure Blossom, Cure Heart, and Cure Flora would all be much weaker then Start of Series Sailor Moon at the start of their series, with Cures early on scaling mostly to Smile PreCure while already heavily battle worn surviving the Bad End Cannon that can destroy planets and numerous early season light speed feats, which is good but still dwarfed by fodder characters in Sailor Moon. The odd argument is that being a Cure comes with a level of supernatural combat skill as well and if you think they can dodge around a bunch they might be able to just outwait Sailor Moon depending on if you think Sailor Moon at this point can tap into the infinite energy of the Silver Crystal for stamina or not. I think it's very unlikely given the speed gap and the fact that the ultrasonic crying is an omnidirectional attack. Cure Heart by the end of DokiDoki PreCure should at least be able to beat this Sailor Moon though as she fought a universal threat and was outright compared to the Big Bang. 

Yuki Yuna: So Yuki Yuna has stats that are neglible compared to Start of Series Sailor Moon, that said even by Episode 1 has fairies that give her immortality and barriers that protect against things like black holes and arguably against universal deities. Basically a fight between them depends on if you think Sailor Moon has some way around this and if not who has higher stamina. The Heroes have enhanced endurance and should be able to fight longer unless Sailor Moon once again can draw on the infinite stamina 

Yugi Muto: So Yugi has some very interesting hax that could hypothetically beat this version of Sailor Moon. On the other hand she can hit the spirit with her Ultrasonic crying. It really just depends on what you think they do in character. I very much could see start of series Yugi appearing ominously and being all scary and that causing Usagi to cry and destroy the spirit. If he appears more normal, I am not sure what would happen. 

Kratos: So it depends on whether or not you think Start of Series should include the Prequel Comic. Prequel Comic Kratos isn't doing anything to Sailor Moon. On the other hand if you think it includes all of God of War Ascension, the first game in the timeline then yeah Kratos should probably win. The Furies have similar feat to the Jadeite dimension with their own dimension, Kratos has similar speed scaling far faster then light, he has own strong suite of abilities plus far greater endurance, skill, etc. If you think it's Kratos from the start of Ascension that gets wonky with Ascension going back and forth in the timeline but Kratos would still have gotten his training from Ares and be likely on that level physically, just lacking in abilities in which case it's might get arguable as it depends on if Sailor Moon's better abilities would be better or worse then Kratos being an actual fighter with extreme skill and endurance in comparison. 

Superman: So would mean Superman at the start of the Golden Age. Superman doesn't get feats on the level of even Beginning of Series Sailor Moon until near the end of the Golden Age so it really depends on whether you think Superman got stronger during the Golden Age. His feats are definitely way way more impressive later on then earlier on, and he does have at least a few points where he seems to struggle with things early on. That said when three Kryptonians come to Earth during the Golden Age, they instantly have powers equal to Superman's, suggesting it's an on/off switch type thing. If Superman has full Golden Age scaling then he would have stellar level scaling and speed feats likely millions of times faster then light and should just blitz. If it's just the feats he has early on then he is negligible in comparison. 

The Five I feel probably could win even at the start of their series:

Bayonetta: Start of Series Bayonetta is trickiest because it's not clear how much losing her memories weakened her, her but she was still able to fight Jeanne without her memories, and if she has any amount of her stats she's either comparable or superior to Beginning of Series Sailor Moon. Even with just comparable speed she can shift into Purgatory and outlast her

Panty Anarchy: Panty doesn't seem to get much stronger during Panty and Stocking meaning she scales to the Silver Surfer parody ep in Season 2 that involves MFTL scaling and arguably universal scaling which should let her beat Start of Series Sailor Moon

Blossom: Blossom doesn't seem to get much stronger during the Powerpuff Girls and so should scale to the feat of making a dimension with a sun that HIM makes which you would need a higher estimate of the Jadeite Dimension feat to beat, as well as to MFTL+ feats of fighting expotentially increasing nanobots and crossover scaling to Monkey's billions of times c feat

Wander: Wander from Wander over Yonder also doesn't seem to get much stronger and in season 2 plugged a black hole that was sucking in the galaxy with his finger. If Sailor Moon was faster she might still win via Moon Tiara but Wander seems at least vaguely relative to Sylvia who can run galactic distances quickly so probably not

Amaterasu: Amaterasu from Okami is the only one who doesn't cheat by scaling to later series feats here. But Amaterasu at the start of Okami can make stars with just a dab of the celestial brush and scales to its MFTL speed, putting her at similar levels to the stellar level interpretation of Sailor Moon just much more casual, and has her own suite of abilities and combat skill. 

On Star Seeds

 

So this was actually a blog I was asked to do. Star Seeds are a concept in the Sailor Moon universe, and one that gets the most discussion powerscaling wise. What do they equate to, what are their properties and how do things related to them work when compared to characters from other series? This blog will not be super powerscale-y per se, this will be just a general analysis and explanation of Star Seeds. 

This blog will be seperated into four sections: Background, Nature, Function, and Narrative. If you want to skip to a section what these will entail are:

-What is the Basis of Star Seeds

-What are Star Seeds

-What do Star Seeds do

-and What is the Narrative Purpose of Star Seeds

Background:

The first thing to know is that Star Seeds are not an idea Naoko Takeuchi made up. Naoko incorporated numerous Mystical and New Age type elements into the Sailor Moon universe. Some examples of these would including Fire Reading

Dowsing

Psychometry

and many many more. 

These Mystical/New Age Notions are similar in that they are believed by a more occult/spiritualist community but are not believed in by Mainstream Science. That said it's clear that in the Sailor Moon universe these practices are actually real. Star Seeds are one of these belief systems. Like many of these New Age beliefs, Star Seeds do not have a singular description of what they are, but numerous. 

The oldest reference comes from Brad Steiger's 1976 book "Gods of Aquarius" which introduces the concept of "Sky People" or "Star People" described as being from Indigenous American accounts and comparing them to that of European Fae

Brad Steiger accounts how he and his wife were adopted into the Wolf Clan of the Seneca Tribe and learned more information on the Star People, namely that there was coming a time of great purification of the Earth but that their Star would assist in the survival of humanity and their uplifting to wisdom and "the path of peace"

The chapter primarily deals with the explanation of UFO Phenomena. When discussing possible external explanations for such beings, the author expresses them as higher dimensional, as intellects and consciousness that are higher forms of being taking on human personage

I can't link every account of Star Seeds but as the concept has evolved, it has become more and more general, that Star Seeds are people from higher dimensions or planes of reality, who take on human form to guide humanity. 

This for instance is the most popular video on the notion on Youtube. They are described as "residents of higher dimensions that incarnated into a physical human experience with the intention to help raise the collective consciousness of humanity" It is stated that the determination if one is a Star Seed is "to look within and determine if they feel a very strong mission, a very strong purpose towards being able to help heal the Earth as well as raise the collective unconsciousness." They are also noted to reincarnate into the Earth system numerous times to better understand the human condition. Other traits commonly noted in this video and elsewhere are that Star Seeds are higher in perception and often eccentric. 

What does this have to do with Sailor Moon? While Naoko Takeuchi doesn't use the concept exactly the same, this should give a good idea of what she was invoking when she used it in the story. In particular while everyone in the Sailor Moon universe has a Star Seed, the archetype of Star Seed is instead something Naoko evokes in the Sailor Senshi:

The Sailor Senshi are girls born with unusual abilities and are outcasted usually because of them:

=

However the Sol Senshi are all good souls:

They reincarnate across lifetimes but have to awaken again to their true identity

This true self is actually a deeper metaphysical self 

They came to this system not just to guide humanity but specifically to guide their evolution by removing negative influences

The parallels go deeper but I hope the point is made. Naoko clearly is very interested in these New Age-y concepts and took inspiration from the Star Seed concept when writing the Sailor Senshi. 

Nature:

Star Seeds have been in the series since the very beginning with the series central Plot Element, "幻の銀水晶"/"Maboroushi no Ginzhuisho", roughly translated "Legendary Silver Crystal" being a Star Seed. However our first descriptions of them as a group are from the Fourth Arc, and it is only in the Fifth and Final Arc that they are explicitly described.

They are first described in a flashback sequence by Queen Serenity to a scared young Princess Serenity. Queen Serenity says that within each of our hearts is a star and that in order to defeat those who's heart is dark, one must keep their star shining brightly

Later in the chapter in a very clear call back, Mamoru says that now that his Golden Crystal has awoken, he feels as though a star was born inside him, and Usagi describes it as the Star of his Heart and the warmth he feels is the sign it is shining brightly

This is a poetic description obviously and is the first expression of what Star Seeds represent, the light in one's heart that allows one to persevere. 

 The final arc has more explicit descriptions with the primary description of Star Seeds coming from Yaten. She describes them:

"Everything in the Heavens grows from a Star Seed. And not just Stars. They come in all shapes and sizes, and they have different names but everything with life grows from a Star Seed."

On Sailor Crystals she says that Sailor Crystals are born as Special Star Seeds. Those seeds are sent off to their Chosen Planet to develop alongside it eventually becoming its Sailor Senshi

Finally she says directly that everything that makes a Sailor Guardian is contained in their Sailor Crystal, that they are distillations of unknown power and will never fade away. 

So to review some of the points Yaten made and expand upon them

Are Star Seeds universal? 

Yes, everything has a Star Seed including, it would seem, the Cosmos and Chaos themselves

The only qualifier is that everything "with life" has a Star Seed. This probably doesn't mean biological life as planets and stars possess Star Seeds but instead life as in vitality or animacy with Celestial Bodies in the Sailor Moon universe being animate

Are Star Seeds Metaphysical?

So, this is a surprisingly interesting question. Yaten says that they are the Distillations of the Senshi' Power. Other translations render is as Crystallizations. The notion there is an immaterial thing that is rendered physical. In other words there is a metaphysical star within the hearts of people and when removed from them crystalizes into a physical form.

We see this exact thing happen in the first arc.  At the death of  her true love, Princess Serenity cries a tear in which there is a light that crystalizes into the Silver Crystal

This is as described earlier the Star of Usagi's heart leaving her body and crystalizing.

The light then leaves the Crystal and enters into Mamoru's body, leaving the Crystal a dead stone

This Crystal component, the shell that housed the light of Usagi's heart is clearly physical. Kenji a normal human is able to physically handle it fine

However the underlying thing INSIDE the Crystal is not material, as shown it passed into Mamoru's body without physical resistance. 

So in other words, Star Seeds are the physical crystallizations of something immaterial within someone. The shell component of a Star Seed can be physically manipulated but the immaterial part, most often conceptualized as a "light", can't be. 

What are Sailor Crystals? 

Sailor Crystals are special Star Seeds that Sailor Senshi have that sent off to their chosen planet to guard them. Those with Sailor Crystals have a special aura of stellar energy

and women with them are Sailor Senshi and can transform into a Sailor Senshi form. 

Sailor Crystals are consistently noted to be the most powerful of the Star Seeds with the greatest shine of them and for those of the Shadow Galactica who worship power they therefore consider them the ultimate or higher class of Star Seeds

Though non Sailor Senshi can have Star Seeds with nearly the same power and radiance as Sailor Crystals

Men can possess Sailor Crystals but are not Sailor Senshi, and cannot transform into a Sailor Senshi form, though can access their Sailor Crystal's power

What is the Lifecycle of Star Seeds?

The final thing of of note from Yaten's description is that Star Seeds will "never fade away." There is a recurrent dichotomy between the temporal physical forms of people and their eternal Star Seeds throughout the Stars Arc and will form the basis of Usagi and Galaxia's philosophical conflict I will talk about later.

Star Seeds like all things are born at the Galaxy Cauldron, a Cosmological Structure in the Sailor Moon universe. Within it all "stars and possibilities" are born

Galaxia herself describes it as the place as the birthplace of the planets and stars of the galaxy, clearly using stars not to just refer to stars as the celestial bodies but also persons via their Star Seeds as indicated by her expression of "Scum and Sailor Guardians." before mentioning that it is where they also pass away

Thus it would appear that Star Seeds are born at Galaxy Cauldron and should they return, they are extinguished. Otherwise they are eternal. If you are wondering about the odd emphasis on the galaxy I will write an addendum about that at the end of this blog. 

Outside Yaten's description, do we know other things about the nature of the Star Seeds? Some. 

Are Star Seeds aware?

Star Seeds, or at least Sailor Crystals seem to possess animacy and awareness themselves. The Silver Crystal has been known to act to protect Usagi and even people close to her even when she is unconscious or even dead

Sailor Senshi can have unusual aging where they don't age for 900 years or rapidly age for an upcoming crisis

This seems to be a function of the Sailor Crystals. 

Do Star Seeds change?

The Star Seeds are eternal in that they don't die naturally, but there is some level of change, usually in correspondence with the state of the thing connected to them. It is noted that they grow alongside their planet

When a Sailor Senshi develops as a person particularly in a way that develops their sense of self the Crystal seems to develop as well such as when Sailor Moon was in despair at feeling like she was alone causing the Silver Crystal to develop into a Lotus shape or Chibi-Moon beginning to step out of her mother's shadow causing her Silver Crystal to become the Pink Moon Crystal

and of course their most famous part, the legendary shine of the Star within. This Shine corresponds to the Star of one's heart and whether one keeps bright

When the body and mind connected to a Sailor Crystal is destroyed, this light is faint. This status is compared to something like sleeping, presumably the Sailor Crystal waiting for the reincarnation 

 

Are Sailor Crystals Souls/Minds?

No, we see them very much contrasted. Souls in Sailor Moon have a humanoid appearance and the Third Arc clearly differentiates them from Sailor Crystal with sequences such as Chibiusa's soul holding her Silver Crystal, her Star Seed

and as mentioned the Star Seed persists though goes into a state of dormancy if both the body and mind are destroyed. 

I believe it is most likely Star Seed should be seen as something conceptual in nature as even conceptual entities like Chaos possess one, showing that even an entity of that level of fundamentality possesses a Star Seed. So what are Star Seeds?

Can one have multiple Star Seeds?

Surprisingly yes, and this actually brings up one of the most important pages for thematic analysis of the Stars Arc and in my opinion for understanding Star Seeds in general

Sailor Galaxia notes that the Sailor Senshi bear two both a human Star Seed but also a Sailor Crystal, wondering at how they cling to their human Star Seeds when they have the unrivaled Sailor Crystals. She demonstrates the difference by destroying human Star Seeds when she uses the Cauldron to destroy Sailor Crystals.

This to me is the key to understanding what a Star Seed is meant to be. What does a Sailor Senshi have that a normal Human only has one of? The answer is something to the effect of "Identities." There's a lot of thematic stuff surrounding this in the Fifth Arc which I will get into the fourth part but here see we what I believe to be key to understanding Star Seeds. The Human Star Seed of the Sol Sailor Senshi represents their Human lifespan while their Sailor Crystal represents their eternal life as a reincarnating Cosmic Guardian. 

Function:

So what do the Star Seeds do? This will be a much shorter section because the answer is much broader. A Star Seed determines much, perhaps everything about its person. 

The most obvious facet of that fact is that when Galaxia took the Star Seeds of Sailor Moon's friends, she used the Sailor Crystals to resurrect them as her evil loyal minions. In this monologue she describes the Sailor Crystals and Power which they represent as the only true reality

as mentioned Yaten describes them everything that makes a Sailor Guardian is contained in their Sailor Crystal, a very comprehensive statement that suggests that everything that makes that identity comes from the Sailor Crystal. 

Star Seeds, or at least Sailor Crystals, seem to be associated most often with protecting the person connected to them. In the Third Arc, the villains powers are thwarted as noted several times because the Senshi possess "the light of the stars, celestial protection"

Star Seeds' primary function seems the maintenance of one's existence. 

When one's Star Seed is removed, it causes one to be erased from existence. 

This does not immediately erase one in other time periods, though at least their future self will gradually begin to fade as though there is a delay

if one's Star Seed is destroyed, which for a Sailor Crystal can only be done from the Galaxy Cauldron it not only erases the individual but their influence from history, this can seen when erased in the Galaxy Cauldron and Chibiusa, his daughter from the future is instantly erased

So one's Star Seed maintains and informs one's existence. 

Sailor Crystals also unlike other Star Seeds grant one their Sailor Senshi abilities obviously. 

Narrative:

So I've said I think Star Seeds represent Identities, but what about thematic reasons for such?

So I've written a lot about this in my Sailor Moon act Reviews, but much of the Final Arc is about laying out the dichotomy between Usagi and Galaxia and what they represent. 

Galaxia represents a kind of Gnostic Search for meaning and the eternal in a world full of flawed temporal things. Galaxia is one of the two strongest Sailor Senshi yet she was born on a trash world in isolation without any deeper meaning

unwilling to believe that such a world was her destiny, she sought to find a world worthy of her, rejecting every world she found as unworthy of her and destroying them

When Galaxia questions why the Sol Senshi cling to their Human Star Seeds, she's asking why they trust in something seemingly so temporal and weak. It's actually very important to her emotionally to get Usagi to admit this as she demands Usagi acknowledge that the things she trusts in are just shadows of the true reality

and when Usagi argues the point Galaxia and insists that it's because of her friends that she has power, because of the temporal things Galaxia believes as just fleeting shadows, Galaxia is taken aback and asks in resentment why USAGI is the one with the strongest Sailor Crystal

Galaxia is the anti-Usagi. At the end of the First Arc, Usagi was offered the life of being the new Queen of the Moon by the spirit of Queen Serenity and instead chose to live as a normal girl on Earth choosing her human life over a celestial life

and at the end of the Fifth Arc Usagi chooses again a life of struggle on Earth with her loved ones that remaining in the Cauldron in perfect heavenly existence

where Galaxia asks why cling to their human star seeds, Usagi wishes that their physical bodies would also exist forever

where Galaxia represents rejecting all, Usagi represents embracing all even a future of never ending conflict, even Chaos the ultimate enemy

The narrative battle between Galaxia and Usagi represents the battle between a Gnostic Rejection of the world as a manifested physical temporality with all its flaws in search for an eternal world vs Love and finding a perfected metaphysical eternal reality within it. Galaxia is depicted as searching and ultimately trying to force a perfect world worthy of her to come into being but it is when she comes to understand Usagi's love, a love that would embrace a future of endless struggle that she finally finds that perfect existence in Usagi

The Sailor Crystals in this arc's dichotomy represent the difference between their philosophy. 

Galaxia thinks that only the Sailor Crystals, that the perfect existence is the only thing that matters, powerful and independent and immortal. It's why she doesn't see any meaning in the temporary and flawed. The series makes an allusion to Plato here when it references that the things formed from the Sailor Crystals are just fleeting shadows in comparison to them and indeed Galaxia's philosophy can be said to be parallel to Platonic/Gnostic thinking, a belief and search for an ultimate reality independent of and "flawed" physical existence

but Usagi argues with it, saying it is specifically because of those temporal things that Galaxia disregards that Usagi is as strong as she is 

Understanding this in terms of identities and the choices they made in regards to living a mortal life vs a purely celestial one, and what the arc is saying is that Galaxia only cares about persons in their eternal metaphysical aspect but Usagi cares about persons in the wholeness of their being. This is essentially the difference between Gnosticism as a Christian Heretic Cult and a more Broad Christian viewpoint for instance, the difference between saying only a person's soul matters and that all parts of a person has a sanctity to it including their soul and their body. There are other religious parallels one can draw obviously including to the Japanese concept of Kami, an invisible spiritual presence in all things with vitality and all the parts of nature. 

Because there's a reason that Naoko gave all people Star Seeds as opposed to just making it so that only Sailor Senshi have Star Seeds as the original concept of Star Seeds was. It's because she wanted to emphasize, as Usagi recognizes at the climax of the manga, that all people have a Star in their hearts, that we all are lonely stars seeking to gather together as one, that we all have a metaphysical part of our being

The Star Seed, the Star in our Hearts, represents the eternal part of ourselves constantly trying to reach each other through this transient physical reality we share. This is why the series ends with the marriage of Usagi and Mamoru, representing the Moon and the Earth, the Celestial and Mundane worlds, coming together to form a new future together. 

TLDR:

Star Seeds represent our Identities. Compared to other verses these can be equated roughly to one's concept, or part of one's concept, or something even more fundamental then one's concept if you think the Law of Identity type stuff is more fundamental than a concept. Star Seed Manipulation broadly does two things

1: Having your star seed removed causes you to be hit by existence erasure. To resist this requires powerful existence erasure resistance stronger then at least the Sailor Senshi who can resist existence erasure

2: If someone gets your Star Seed they can use it, or at least Galaxia can, to alter you in basically anyway they want. This is conceptual manipulation. I hear some people call it information manipulation. Personally I don't see this as very different from conceptual manipulation but to the extent it is different then yeah it should also allow for that. Resisting this requires conceptual manipulation resistance

Addendum: The Emphasis on the Galaxy

If you're wondering at the emphasis of the Milky Way Galaxy in Sailor Moon, this is actually because in Japan the "Milky Way" is actually Amanogawa (天の川) which translates more literally to "The Heavenly River." The Heavenly River is a fixture of some Japanese religious traditions as a poetic image. In folklore the Sky King's daughter Shokujo married the cowherd Kengyu but with the Heavenly River created to separate them so they can only meet once per year, an occasion celebrated on Tanabata. This event is referenced directly in Sailor Moon

and is shown to be a true account

Amanogawa in Japan is heavily linked with the expression of love, and particularly a distant or impossible love. In Classical Japanese poetry the flooding or misting over of the Heavenly River was connected with the fortunes of lovers separated by space or fate. A poem from the "The Romance of the Milky Way (Amanogawa)" for instance:

"Though the waters of the River of Heaven have not greatly risen, yet to cross this near stream and to wait upon him remains impossible."

The Stars Arc in particular also takes a substantial amount from other East Asian Cultures for inspiration such as Princess Kakyuu taking much in design from Chinese History and Myth and the Three Starlights Sailor Star Fighter, Sailor Star Maker, and Sailor Star Healer corresponding to the Trimurti of Hinduism. In China while still associated with distant love, it is also seen as a representation of fate or divine authority. Consider the beginning of the Tang Dynasty Poem "A Ballad of Heaven" by Li He:

"The River of Heaven wheels at night

Drifting the circling stars

At Silver Bank, the floating clouds

Mimic the Murmur of Water

By the Palace of Jade, the cassia blossoms

Have not yet fallen

Fairy Maidens gather their fragrance

For their dangling girdle-satchels"

to go back to Sailor Moon, Galaxia considers herself divinely chosen, characterized by the highest of ambition, and her ambition is speculated to be to use the Milky Way to control the procession of stars and their development

As such I don't believe that the character's reference to using the Cauldron to control the stars of the galaxy is meant to be a limiting factor on the Cauldron's influence. Numerous Stars from the Cauldron emerged in other DIMENSIONS such as Pharaoh 90, and furthermore it is said numerous times that the Cauldron can be used to rule over the universe or even to create a new universe

Rather that the conquest of the Heavenly River is meant to represent Galaxia's divine level of ambition, her Luciferian desire to be the Lord of Heaven, that she considers herself to be a God, and perhaps to represent that the way she stole Mamoru, Usagi's love, creating a sense of romantic separation. I wrote about this more in my Sailor Moon reviews but there is a narrative separation between the Earth, Usagi's world which Galaxia considers inconsequential and the "Heavenly" world of Galaxia, the cosmic and eternal. For a comparison it's like a verse based on Greek Myth having characters very focused on getting control of Mount Olympus and getting its power. It's not saying they are mountain level, but that the mountain has a special religious significance. 

Feel free to ask if there are any more clarifying questions I can answer about the Sailor Moon universe.