It turned out to be pretty obvious that Kalani would reincarnate as a wolf — she frees captive wolves at the temple, helps a trapped wolf cub, and one of her last acts is protecting the cub from her father. Her soul might have even gone into that very cub or its descendants.
Kalani didn't need to undergo a redemption quest as a wolf, as she already did it during her human life and received a proper funeral. Atevo however, didn't receive a funeral and was doomed to wander the world as a spirit, refusing to reincarnate as he thought he didn't do anything wrong that was his fault and eventually forgetting that he did anything at all. He dissociated so hard he even became voiced by a different person.
Atevo's insistence on Never My Fault stayed with him as a spirit, allowing him to flip the script and believe he is the one working towards Kalani's redemption. This is only enhanced by his ignorance of his true identity, allowing him to act as a third-person observer and pass judgement onto Kalani.
It's not that hard to catch on that the spirit-companion has to be experiencing a redemption arc of his own: every time you hear the crackling sound that indicates one of the red barriers has become brittle, it's immediately after he's said something compassionate or insightful.
