It's a little ambiguous who the bad guys of RW are -- most of the things trying to kill our heroes so far have just been monsters -- but since this mysterious cult keeps getting in their way I casually refer to its leaders as the villains :>
Master Quentin Agorath (the taller guy with the bandolier of vials) is the head of the cult. He is very good at remembering the obscure incantations and components of forbidden magical rituals, and very bad at remembering things like, schedules, where he got that book from, or where he last left his keys. He should really get some sleep.
Esra (the shorter guy) is his constantly-stressed, overworked, under-appreciated second-in-command, though some of the overwork might be of the "insists on everything being organised when literally nobody cares" variety.
They wouldn't be all that sinister except that due to weird oath magic, everyone in the cult is literally unable to tell anyone what exactly their goals are, and that's, well, that's always a bit suspect.