The day has finally come with Episode 63, as Asta transforms into his Black Asta form in a spectacular fashion and completely wipes out Ladros of the Diamond Kingdom. You can see the ferocity in the clip below.

What episode does Asta go devil?

Episode 162 of the series shows off Dante's terrifying power even before he starts using his Devil abilities.

Why did Asta turn into a demon?

Eventually, Asta was able to channel Liebe's energy through a spell allowing him to become empowered by Anti-Magic while it covers his body, transforming it to resemble more of an amalgamated human-demon form.