I'm still not really a fan of how it turned out, but I cobbled together a (long, edgy, self-indulgent) backstory for Sableye and I'm done fiddling with it. It also introduces an NPC that could be used as a villain in future stories if anyone wants to.
Most of his beef is with Sableye for now, but that's only because he isn't aware of the other humans yet.https://rentry.org/zyw8t