Which is Darkin host is most interesting?

On one hand you have kayn who is willing to take up Rhaast due to his arrogance and ambitions which leads to Kayn pushing himself to win this inner war with himself and Rhaast in order to pursue his grand plans and surpass all. On the other hand Val has dragged Kai into their current arrangement in order to be with him. Now Kai and Val have to pit their love against Varus's hate and grief in order to gain dominance.

Or you could go with the mystery host that is Aatrox's current body.