The monsters that monsters fear.

The closest D&D 5e gets to this is the semi-official class Blood Hunters, created by Matt Mercer.

Eesh. Magic fed by pain and blood seems a bit dicey. I hope they keep a tight leash on their members (no pun or offense intended to the wolves =P), because I don't think I'd trust that kinda thing to just anyone. Though I'm not sure if I'd trust it at all, if I'm honest.

Thankfully, I'll probably never be in a situation where I'll need to make a call like that. I don't think I'm cut out for leadership. I'd need some good people around me to help keep me calm and maybe manage the bits I can't do myself.