Omtose says there may be a cult. However, amongst the list of roles, there's no recruiter or deprogrammer, so I'll ignore that option for now. Incidentally, it casts suspicion on Omtose

Town needs to get rid of all who aren't town.
Ivets will probably have to kill everyone who's not an Ivet.
The possessed? Possess everyone? They would be a cult, but with a different mechanic.
Since the Ivets seem to be a different species (anyone able to confirm?), I doubt they can be possessed.
So, possessed and town share a goal there: lynch the Ivets.
Town needs to get rid of possessed, as do the Ivets? Question mark there, that can maybe be answered by the writer's fans amongst us.
The trick to counter the possessed will be to spot differences in alt's playing styles, I guess. The silent guys will definately get my attention, as they'll be the easiest to take over without us noticing.