I am looking for help to name a fictional species in a low-fantasy setting. There is a sudden outbreak of a demonlike species. The species is capable of possessing people and grant them power. As the possessing doesn't happen via contract and has no visual indication at first, there is no way to tell if someone is possessed or not, leaving the hosts to stumble upon the power by themselves. When the hosts did stumble upon the power, however, the species will gradually take over them. They will start gaining some of the species's physical traits (which vary wildly, some look like humans, some look like monsters that crawl out of the closet, etc), then, they'll start gaining the species's personality (which also vary wildly). In the end, the host will "die", in the way of being erased inside out. They are sentient, and some can be reasoned with, resulting in a partnership. But the "deletion" still applies to them even though the power is given willingly. Ideas?