The darkness that swallowed Athan into nothingness really turned him into literally nothing.
His past, present, and future ceased to exist at that point. Nobody remembers him anymore, and...he found about this at the last moment of his life. He found out this when his half-destroyed soul was being swallowed by the darkness that...Nothing, not even other people's memory of him, would remain.
When that dispair was replaced by another expression at the last moment, this was his thought.
'...Dying horribly in the first life and even more horribly in the second life?...My whole existence, my entire two lives, my happy moments with Tiana, Avelia, and others, the pain I suffered to get strong, the journey and adventure...All these...just lost their meaning? '
His soul was only half left due to purple power destroying it, and even that was engulfed in this darkness. At that moment, He accepted it.