I think Na-In “died” only once and at the verge of death and depression, Amon literally ate him before he probably got “reincarnated” a few hundred years later but now has a part of Amon in him (or is a part of Amon now since he ate him). Na-in only can stay “immortal” as long as humans are being sacrificed and their lifespan is somehow being transferred over to Na-in…and the priest is erasing his memories to keep him from remembering his past life and his hatred for Amon or idk bro

Na-in is human.
Amon is an immortal god
I’m assuming Na-in reincarnates every time he dies and the Amon finds him, that priest does the fucked up ritual that either wipes Na-ins memories, or brings Na-ins memories from his past life, or both! Right?
A theory