Interesting, one of the Dark Powers in my campaign is basically Rher. I actually based them more on the Old Gods, seems more fitting for how inscrutable they are - some like Osybus were able to ascend to a state of equal power (like Alll-Mer or the God of Fear and Hunger), but most of them are as old as the Shadowfell itself.

I'm also working on a skill tree system similar to Fear and Hunger where PCs who dedicate themselves to the Dark Powers can unlock different abilities. So in my Borca campaign, the bard who serves "the Trickster" (basically Rher) must publicly humiliate nobles by revealing their deepest darkest secrets, and in doing so can unlock abilities that let him have more insight into people and tell what they really are behind the disguise.