Were they possessed at the end of the movie? spoilers

Did some evil beings from ethereal realm managed to throw people out of their own bodies and then to inhabit them themselves? And if so at what point did one posses Jim? During his first self-induced death? These beings kinda resemble Demiurge and Archons, evil architects of the Universe, in whom Gnostics used to believe, evil beings from lower fourth dimension which created physical world in order to capture people in it and then to live in material reality through that people's bodies, because they really feel attracted to material world although they are spiritual beings. If the Jim's plan was first to bring them close to death and then to revive them with anti-dote just before death and that hasn't happened, how come his plan still succeeded and they became immortal bodies with demons in them after they died?