[k//eternal]

Spoiler:

More like "accident, poison, trap, animal, disease, or natural disaster". I think it would be massively ironic if Beato's true form was that of a gigantic wolf pack, since her legend replaced the story of wolves in the forest, but it's likely not the most solid theory around, haha.

If you want to roll with Battler being the killer, he can be "killed by guilt" in some sense, as well... although I'm not too fond of that interpretation of "I am not you" so hopefully it's not that.

By the way, there might actually be a clue in the end of Ange's story... weren't there basically "soft cliffs" around the mountain? There could have been a landslide that leads to Battler's death.

The heavy rain makes this more likely to happen, too.