From what we know, there are two main natures -- blue and orange -- that are constantly at war with each other. Once one wins over the other, the victor absorbs the loser, taking their energy and shifting both of their forms. They then swap natures, and the victor goes on their way while the loser bums around, probably out of exhaustion or smth. Blue starfolk tend to have either lightning or ice natures, while orange starfolk favor wind and fire (because colors~)

However, rarely, the absorption results in a sort of merge where the combatants fuse to become a single green starfolk. This is where Adaptation, Duality, and Yin-Yang come from, and you can see it happen in the Eastern area of the map. If I remember correctly, it's a crescent and ariman(?) that forms Quimera.

These merged starfolk gain an incredible amount of power, as the most powerful enemies in the game (*cough* Summum *cough*) and can be assumed to be a sort of ascendance, as they no longer obey either of their original natures. Also, from the character designs, it appears that the more green a starfolk has, the more powerful and "near-perfect" they are, hence the extreme difficulty of Summum's fight. The sole exception to this appears to be Edda and Aven.

While yes, Duality has two individual, fully-functioning parts that each have at least some independent thought, Edda and Aven are two completely separate beings. They are physically separated, even though you never see them next to each other unless it's in cutscenes or in special moves, unlike Duality who clearly merges to perform their giant star attacks. Part of that is logicked away to the functionality of gameplay controls, but still. There is no evidence of their merge until they touch, in which green light covers the screen, or the giant sword from Unified Division appears. We are clearly told that whatever they have going on is special in a way that has caught the eye of what is closest to a god in their universe (which is a whole other can of worms that I'll write about later). Either way, they're much stronger than the traditional green starfolk, as seen by the fact that people can beat Summum in 4 minutes *Gestures at speedrun video*.

Now, I also want to touch on whatever the heck is up with Edda and Aven's absorption. We can see in the background -- within 3 minutes of starting the game -- that whenever a starfolk is absorbed, they swap natures and are distorted beyond recognition. However, whenever Edda (and later Aven) does the same, they remain perfectly untouched while the enemy is completely obliterated. I, personally, think this is an ability granted to them following Aved's failed absorption of Edda at the start, where the two are something like a "ever-strengthening" or "consuming" being like how Adaptation is the "ever-changing" and Yin-Yang is the "stable yet unstable" being. Their initial merge is also probably why their own kinds attack them, which took me embarrassingly long to realize.

That's all I can really think of at the moment, but I might write more later.