Thanks for all the info! Here's my thoughts in no particular order:
I personally would prefer if he were over 18 because I'd feel a little weird having a member that might be like 14-15-16 you know?
The background works, considering they would probably feel his negative energy and be drawn to it.
The cult doesn't have any scientific evidence but I mean, when they sacrifice stuff it bursts into a puff of dark magic with a big extravagant process so I m e a n, if he showed any signs of disbelief Chrysma (my OC) would probably train him personally.
Honestly that works, considering one of the BIG things of the cult is gathering power, be it through artifacts, spells, etc.
The cult isn't JUST about killing people, it's about killing people that have POWER, so they probably wouldn't set a village on fire for the sake of pyromania, but maybe for the sake of activating a hidden power or drawing out the town sorcerer.
I would prefer that you didn't steal from the cult, as that would cause a lot of inward tension, and the main tension we want here is between the White Hand and The Hands of Abberoth as we have it set now. As we talk, this might change though. So think of a "probably not" rather than a definite no.
And I didn't mean you SHOULDN'T make one, I just meant it wasn't MANDATORY. Go ahead and make a character sheet if you want, I'd love for you to enjoy this as much as possible.
One big rule I forgot to mention about this RP:
We're here to have fun! The only time we're doing it wrong is if we're going off canon, and/or one or more of us isn't having fun.