Ancient Nordic. I'm disappointed that so much of the religion was so Cyrodillic in Skyrim, but I guess that makes sense given the history between Cyrodiil and Skyrim with all those centuries of Imperial rule. It's still a little jarring seeing Nords killing in the name of the Old Ways for the return of Talos Worship while revering the benevolent Arkay over Old Orkey. Some of it remained like Mara's position as Kyne's handmaiden, but it wasn't enough for me.
Fermented bee barf please.