Lowkey spoilers don't know if I'm right...
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So I read a LONG time ago I don't remember most of it but Na-in was originally a human and Amon fell in love with him at first sight... but Amon couldn't understand human emotions like pain , grief , suffering. Also Amon's original form is that of a dragon. So when Na-in dies and Amon revives/ reincarnates Nain and made him a Shah , lots of Leshah's died in the name of Shah . After seeing so many people die for him Nain got really depressed and suicidal lowkey (if I'm not wrong) Amon couldn't understand why Nain is so mentally disturbed from seeing humans dying cuz as a dragon humans are literally worth nothing to him and he feels no emotions whatsoever expect his attachment to Nain...So Amon made a deal with that old man's family that if they can hold a ritual to erase Na-in's memories then Amon will leave all the power of leading the country to his family cuz Amon wanted to do nothing with the human world and all he wanted was to keep Nain alive...So indirectly that old man's family is ruling the country.
(I know there is quite a loopholes in my memories but as much as I remember, this is the basic idea)
I wonder how tf does this benefit that old mf