I am halfway through the ep rn and I'm telling ya, if anyone except Asta can use the powers of the devil Asta can use I am gonna fucking slap the hell out of the writers. My personal opinion but I would hate the legit one thing Asta does be done by some run-of-the-mill wanna be devil ass-kissers
Bruh legit the only original thing about Asta is being stolen by random peasants. If someone actually strong or that other devil does it, no problem. Something monstrous like possession or something like Naruto in his Kyubii form before he could control Kurama is still ok but just not something like what Asta does. Personal opinion and probably uncommon but nonetheless.
Asta is the only one who can use his specific devil because it has anti magic and anyone else would die from having their magic absorbed. There are other devils with different magic that can give their powers to other people.
because it's not filler and people who are serious about it are stupid and don't know what 'canon' means. but I respect that you think this is filler but aren't complaining openly hope what I said informs you well