Arfoire (EntityTopic, 7)
From Compile Worlds
Arfoire is the main villain of Hyperdimension Neptunia Re;birth1. It's still unknown if she is or is connected to the Mysterious Instigator that kicks everything off, but she's responsible for creating the Enemy Discs that fill the world with monsters, setting up the evil company Avenir to develop a silly amount of military weaponry and robots, impersonating the goddesses and various other people, popularising the idea of the oh so scary Overlord Momus, and just generally being a complete bitch. Neptune even nicknamed her the True Loner, the culmination of a running gag in which Noire gets called a loner a lot.
Histoirery
Apparently, Arfoire used to be a good person, and was the one who raised the four CPUs, though was not the same person as the former goddess who was their mother. She has little power of her own, but the power she does have is the power to copy; she is able to steal the powers of other characters, though sometimes said other character loses their power and other times they don't, and sometimes they are able to snatch it back from Arfoire and sometimes they aren't - there doesn't seem to be any rational explanation as to what makes the difference, other than what's important to make the storyline work. Anyway, at some point, the power took her over and thus she stopped being a good person. Eventually, at the end of the game, she even ditches her human form and turns into a dragon as she has been completely corrupted.