There seems to be a bit of confusion over how the Volans work and the alter egos. Some of this is by design. There should remain some mystery about these things as the MC and other character learn, so will the players. But somethings have been made fairly clear in the game, but perhaps got a little lost in translation or in the episodic realize format. This is all just how things seem at this moment, and things may be made more clear, or even turn out differently from the concept here as more in game information is presented.
The Main Character, Lucas, Megan, Gabriella, and Mia all have Volans. These are separate being that basically live inside them and talk to them. Empowering them but also feeding off of them and gaining power from them. That power can be gained in several ways. The two we have seen explored most in the game so far are lust/love (often expressed through sex) and fear (often expressed through violence), but other emotions can power them too, like greed. Think of Volans like emotional vampires. Feeding off strong emotions of those that are tied to the person the Volan dwells inside of. As far as powers go, they can grant seemingly supernatural abilities, like we see Mia use to toss the mother across the room. The MC hasn’t really had a chance to use those powers yet.
One power that Volans have is in their ability to basically implant or unlock an alter ego in people. Alter egos are a little part of a person that the Volan empowers in them. It makes them more receptive to the powers of the Volan and their vessel. It also basically claims that person for that Volan. Think of it like unlocking a person’s subconscious and bringing their true self to the front. It isn’t a separate being, but just a part of a person give a voice by a Volan that dwells in someone else. This can be a good thing or a bad thing depending on the person. Chloe embraces her desire for her brother but also got her “bad bitch” persona amped up to eleven. Her alter ego is the most fully realized at this point. It remains to be seen how the other girls alter egos will ultimately affect them.