There is lore about the Ancestral Spirits and the followers (the ghost minotaurs). It's on item descriptions and such, which is kind of par for the course with From Software.Also the story is still incomprehensible. I fought and eventually got gud and killed this ancestral deer spirit ice god boss thing, and I will say its a gorgeous boss fight. Just hands down one of the best looking boss fights ever and my clear standout for best Elden Ring boss so far. That said, I have no idea why it was on a bridge in a secret underground world, no idea why it teleported me to a giant cavern, no idea why its hostile, no idea why there are ghost minotaurs around, no idea why killing the ice deer god lets me summon minotaurs now, and the deer god wasn't even guarding anything. Its a dead end, no pun intended. You kill the boss, get a random power, and then leave. No explanations, no dialogue, no hint of a story or plot, no reason why we fought or anything. And I feel let down. Great boss fight, great ascetics and feel and music and the dancing blue deer galloping in the sky was beautiful and then nothing. It's just over and the game is like "On your bike, nothing more to see, you must not dwell." and its like...wat?
Besides, this ain't new. People still don't really know what the fuck The One Reborn is. And that's a main story boss.