So anyway info dump on how RP!Fen's magic works.
Since there's no real explanation in the games. I had her explain earlier but I'll put this here for Badge's benefit.
Fen's cells each have a tiny generator inside of them that produce demonic energy which is stored in her cells untill she needs it. At max capacity when its doing nothing but keeping her body warm there's enough to keep her going for a few days. It can be channeled to do things such as turn her sword into a beam saber of to power magical artifacts. It can also solidify the air around her to make a barrier or platform. She goes into Devil Trigger by infusing herself with it rather than just storing it though she has not mastered doing this yet.
PM box is Closed, Indefinitely Friend Code: 3368-4181-6850With that in mind I think it might explain why Nero's Devil Bringer is the way it is.
Its possible that cells in his arm are mutated in that they don't have a "storage unit" and the generators are overclocked so that they constantly produce not only the energy needed to maintain the transformation but also to project the ghost arm.
/shit nobody cares about.
PM box is Closed, Indefinitely Friend Code: 3368-4181-6850

the bastard