With all the Darkin so far, we've seen a lot of discord between them. Varus, Aatrox, Rhaast etc. What if we got Darkin who had a host that completely welcomed them, instant of hindering them or having any conflict between the two.
As much as I hate to use Naruto as an example, it's the best one I can think of. As strong as he was when he used the nine-tails power, it was absolutely pathetic when they came together completely, gaining a new power that rivaled the gods of their world.
So what if there was the same thing that happened with a champion and a Darkin who completely worked in sync with each other?