I've been wanting to do a plot involving Darin's 'other half' getting out via gem corruption/cracking. I don't really have a ton of details on it yet considering this has been a very very slow build, but the long and short of it is:

Darin hasn't gotten any new gem powers since he returned to the game and I've been doing that intentionally. He's been suppressing any and all powers out of fear he's going to change into an Archfiend and destroy the world. Suppressing his powers like this is obviously not a good thing and eventually, the strain is going to cause his gem to crack, corrupting him and releasing the Archfiend soul inside of him. This is a big deal because he has half the soul of a god of destruction inside of him! So, aside from all of that, that's all I've got and I'd love to have some CR build up towards this!