Biologically, I consider Pyronites agender at default (inevitably by process of space travel and meeting cultures in which gender is prevalent there will be Pyros who think social gender sounds awesome actually and promptly trans their gender), we’ve only seen Pryonite transformations and hybrids as full characters, leaving them up for interpretation in my opinion. Any two of the species can mate, in which they will mutually erupt in flame until a rocky body is formed from their combined material and a fire inhabits it.

(Which results in a very interesting kink scene for other species with a thing for burning)

Vulpimancers lack a social concept of romance. Which in a way means they have an aromantic society but also not because they have no reference of what romance is to consider themselves devoid of it.

Necrofriggians are an agender and sexless species we all know this.

Anur Transyl has a very prominent queer scene, it effectively goes hand in hand with accepting so many different cultures as a multi species planet.

On that note, Ectonurites are a sexless species that reproduces via apomixis. Though they do have a cultural understanding of gender that translates to our understanding of m/f, but it has nothing to do with anything related to reproduction.

Tetramand culture has a very prominent f/f culture in its history. Many of female Tetramand that were unable to be defeated by any man were instead eventually bested by a woman and were promptly betrothed. These pairs were typically renowned as images of strength. M/m couples took longer to be accepted, unfortunately, initially being regarded as both partners being too weak to court a female.

Polymorphs are biologically sexless and socially genderless. Single cell organisms don’t have much to work with.

Lepidopterrians are a tri-sex species. Sexualities are thought us which of those the individual is attracted to. Three for exclusive attraction to each one, three for any combination of two of them, and one for attraction to all and any. Which of the three the individual happens to be is not considered.

Piscciss Volanns have the natural ability to change their sex when their current environment necessitates. Now however, it is used also as a way to transition for bodily dysmorphic transgender Volanns. Due to the larger size and different physicality of the females compared to the males, it’s a long and rather strenuous process, but is met with much celebration when completed.

Planchaküle treat genderfluidity as the default. They love their adaptations after all. Can’t leave one thing as it is for too long.

Methanosians have four sexes. Two which produce pollen, pollination functions with only one of them providing the pollen, but the two of them joining together in the act results in more diverse offspring and is the social norm. The other two are the pollinated. The first of them will always bare offspring of the two pollinator sexes, while the other will always bare offspring of the pollenated sexes. Perhaps not the most streamlined reproduction cycle but it seems to be working for them.

Cerebroian Currmary all default to male as a result of their biological programming. This was unintentional of the Cerebrocrustians, but they would claim otherwise. Many decide they prefer to be female, neither, or both however.

Galvanic Mechamorphs don’t have sex, but they do base their gender off of the Galvan’s because they think it’s neat.

Kuphulu

In reference to this post-

The 'having a favourite fictional setting' to 'make a conlang' pipeline is all to real Pilgrim, my linguistics teacher let me use mine for my end of term project instead of the assigned analysis (transcribing a conversation between yourself and a friend, which probably would've been useful to study); you wouldn't believe what planet I based it on (don't look at my icon that's cheating :P)

But nah yeah, the Anur System is to me one of my favourite parts of Ben 10 Omniverse since I love horror and horror themed things but hate being scared of them so- the Anur System and the movie monsters that influence their design always has a special place in my head!

Okay, so you know how Ghostfreak looks totally different from Zs’Skayr because of all that white stuff around him? I see it as sort of a protective film or blanket that wraps around the vulnerable body of an Ectonurite. Since they’re weak to sunlight, Ectonurites are born with this protective layer. They hold onto it pretty tight when they’re young since that’s when they’re most vulnerable but they shed it when it gets older.

I think at some point it falls off naturally if you don’t care about it but I like to think that at same age Ectonurites just think they don’t need it anymore. They get hot headed and think that they’re strong enough to make it in the world without it. Most Ectonurites live sheltered from the sun so I’ll bet a lot of them don’t actually know how dangerous it is and think that it’s something they can shrug off or tough out.

I can see young Econurites loving their white skin like how a little kid loves a baby blanket but as a teenager, abruptly decide they don’t need it anymore or think they’re too cool for it. This probably leads to some peer pressure to shed your skin before you’re ready. Maybe on different planets and towns in the Anur System, there’s different expectations as to how long you can hold onto your skin.

Share-Oh

Y’know, the mummy alien. Has wrapping powers.

Blitzwolfer 

I decided to make the Loboans from Luna Lobo different from the Loboans that live on planets such as Anur Transyl. Blitzwolfer is the same as Omniverse. He is a Planetary Loboan. Planetary Loboans are physically stronger, can run faster in short distances, and their howls hit a bit harder. Lunan Loboans are leaner, smaller, wilier, can run longer, and their howls serve more as communication than a hard hitting attack, though it still hurts, but they are the same species so Rook is only able to transform into the one his DNA sample came from.

Ghostfreak

Ghostfreak functions for Rook the same as he does for Ben. He does not look like Zs’Skayr does. In this fic, I am explaining that as Ectonurites are born with a protective skin that they shed as they age, so Ghostfreak is just a younger Zs’Skayr. I explain that theory more in a supplementary post linked on the series page on Ao3.

Whampire

I’m not quite sure how Rook got this form but assume something happened during the time skip or the Omnitrix was able to scan the dormant Vladat guy.

Frankenstrike

Like in canon, Frankenstike is a heavy hitter with limited electric powers.

Pumpkin Head

Remember the mutant pumpkins outside the castle? Yeah, the Omnitrix scanned those guys. Note that the pumpkins only became jack-o-lanterns when Ben tried lighting them on fire. When Pumpkin Head first appears, he won’t have any fire.

Brain Drain

Brain Drain Tom Perkins alien designed for the Anur System. I believe they play a role in 5YL, though I haven’t read the comic yet. They’re essentially energy draining zombies.

Night Mare

In the Omniverse episode where the women in Ben’s life competed for him, there was a race on Anur Transyl and Ester found a spectral horse. They are listed as Night Mare on the wiki so I’m giving Rook one. Their powers include phasing through objects plus normal horse stuff.

L’Goon

Another Tom Perkins alien. L'Goon is a fishlike water-based lifeform from Anur Millgan. His powers include the ability to control and shape water.

Skele-TON