Babadook champion, because i just saw the movie
Champ concept very vague
this champion would essentially work by 'maddening' a target enemy would, for a short period of time, be targetable by their team, and then babadook would take direct control over them. this ability would essentially be his passive.
Babadook would build up his control over something with his various other abilities.
Babadook would also have the ability to mirror the appearance of an enemy player, taking on all of their stats except for ward skins, during this time babadook can use chat and appear as that enemy (To the enemy team) and can deal illusion damage to his team, illusion damage is essentially fake damage. It looks as though your enemy renekton has taken massive damage, but then maybe when your zed dives him, it turns out he was full hp alll along
he would also have the ability to drop fog of war, which would essentially make it so that any enemy outside of a zone can't see what happens within it
finally babadook would have the ability to bink short distances