Alright here's mine, GEAR ATTUNMENT. Also called gear mastery or just mastery, is a phenomenon where, after vigorous training or a life of death scenario, an inphernal can attune to their gear and access powers they couldn't pro form normally like swords blade beam. Deities can't attune to their gears, they were spawned at full power, this transfers to their offspring, with demi-deities having less powerful attunments. Artificial gears and modified gears can't be attuned to but an already attuned gear can be modified. And yes curses can prohibit attunment.
this reminds me of gachiakuta (/VVPOS love that anime to bits), yoinking this hc!! love that it explains sword's blade beam tbh like yeah how DOES bro have that. twin out here casually spawning a windblade type shit LMFAO