established relationship. hux wants kylo to brand him with his lightsaber (hux gets off on the pain?? he gets off on the idea of being marked as kylo's?? up to you). kylo is reluctant about it at first but in the end they're both massively turned on by the act and have the most passionate, mindblowing sex ever afterwards. bonus points if kylo bites/licks the burn mark he's just left.