What do the spells Ascension and Ascension (Corgayle) do. All the civilopedia says is one can only be cast in cities. Also is the dragon you can wake with Stir From Slumber only for people with the White Hand religion? I googled Mulcan but couldn't find anything
Yeah, the Civilopedia is a bit incomplete here, but you can still work this out. I already answered you on Ascension and Ascension (Corgayle). As for Stir from Slumber, the 'pedia entry says that it gets you Drifa the White Dragon. The entry for Drifa says that it requires White Hand. So Stir from Slumber requires White Hand. Might help if the entry for Stir from Slumber -- as well as the entry for The Deepening, for that matter -- specified that it required White Hand, to make things a bit clearer. I sometimes forget which of the winter rituals require White Hand and which require Illians (or Frozen), because in regular FfH2 the White Hand is an Illians-only religion, and the Illians can't research or adopt other religions, so there's no distinction among the winter rituals. (The Frozen weren't in original FfH2.)
I see some animals units say "Cernunnos" on them. Is he an aI player or a god? Is there any way to make peace with him/her? Will building the building that "makes peace with animal packs" have any effect with animals controleld by Cernunnos? Or none?
I know you got a partial answer to this, but here goes some more, since this is something the Civilopedia doesn't really explain, I don't think. The Barbarians in this mod are split into different groups -- I think that started back in Fall Further, where they decided that it didn't make sense for all these different Barbarian units to be part of some undifferentiated Barbarian State. So you have the Animal Packs (wild animals, obviously), whose "Leader" is Cernunnos; Demons (including the Mana Guardians if you play with that option), led by Agares; and Savages (Orcs, Giants, Centaurs, Goblins, Cyclops, and "regular" Barbarians), led by Bhall. I don't know if it was programming reasons to give the different Barbarian factions leaders or if it was more aesthetics/ flavor.
So if you see notifications about making (or being at) peace with Bhall, Agares, or Cernunnos, this is what they're referring to.
Only the Savages can occupy and hold a city after capturing it. If the Animal Packs or Demons capture a city it's razed. I think I remember reading that this was a programming matter, that you couldn't have multiple Barbarian factions owning cities, something like that.
Similarly, diplomacy with the Barbarians isn't really doable -- again, something to do with the code. I'm not a programmer, so can't provide details.