I'm not really sure I'd call Believers of Fire a higher level version of Red baptist, they seem pretty different to me. In addition to the summonable creatures already mentioned, Believers of Fire can summon Iron Golems and Cerebus (sp?) which are what makes Believers of Fire nasty, I think. Unlike Baptists, Believers of Fire will walk into melee range before casting spells. I don't remember seeing a Believer of Fire teleporting either.