I see a lot of people saying he should get a legendary skin etc. I think it would be dope for him to get a whole ass champion.
“Faker, the demon king” or some shit. Would need to low-key look like faker without looking silly / out of place on summoner’s rift. Probably some sort of control mage. Kit should resemble a mix of his signature champions (Ryze, LB, Azir, Ori, good luck balance team).
Back in base they should hang a portrait of him next to the merchants.