I don’t know if I’m the novelisation, there is a big reveal in who he really is? The origin of his immortality and so on. This season reveals the origin of his memory loss, which is my favourite part of this drama.
I’ve had my thoughts on his possible real origins
In my feeble deductions, I’ve pondered the meaning of his name ‘heartless’, his missing heart and his immortality.
Is he the Monkey King? The monkey king wreaked havocin the heavens and was cast out.
Is he the Monkey King, cast onto Earth, wandering for eternity, earning his way back to the ascended plane? Thelack of a heart, I feel supports this theory.
He’s been wandering for so long, he no longer has certain memories anyway, even before he’s bestowed the gift of forgetting, in season 3. I’m thinking he was cast down, CURSED for all his mischief and wrongdoings, unable to forget, as such in eternal torment, with only purpose to seemingly seek his death and unbeknownst to him, his urge to help people is part of his redemption arc.