Possession
Disclaimer: I don't own MTV Scream, MTV and whoever else owns it.
This is what he likes most. Playing games with people lives as well as getting away with it. He gets to be a God by killing people. He enjoyed killing his mother and step-father and fooling the police. An accident. More like he caused the accident but the police accepted his version of the story. The best part of this is knowing he can get away with everything. He was happy destroying his cousin's life. After all, Eli is a piece of shit head (poking his head around for no reason). Eli should have just stopped annoying him but Kieran knows that Eli could never change. And he can also get away with so much. He did get to come to this town and killed his father.
He knows he is charming. And that he doesn't give a shit about people's emotions. He can always mimic people's emotions so well like how he says he cares about Emma. If anything Emma is the ultimate prize. His possession. He can't wait til he gets to put his hands on her. He'll make sure to make her death in an intimate slow way. He likes watching people die. He likes having the power over everyone.
If anything else, he knows he'll win this game. After all, he enjoys hearing all the people he killed in his life their last breathe. That is his possession. And he has to thank Piper Shaw for getting him to start and keep continuing this game.