The Devil's power has been one of the core mysteries through Black Clover thus far, but the newest chapter of the series revealed that it was actually possible to control the Devils and their power. When Yami and Vangeance were kidnapped by the Spade Kingdom's Dark Triad with the intention of sacrificing them to open the gates of the underworld, Nacht, the Vice Captain of the Black Bulls, decided to take Asta under his wing with the hopes to make him into the Clover Kingdom's ultimate weapon by teaching him how to use his Devil's power.
With the Dark Triad beginning their ritual in just a few days' time, Nacht officially begins Asta's training. He reveals that Asta was only siphoning the power that trickled down from the Devil before, but there's actually a way to bring that power fully under his command through a forbidden ritual known as the Devil-Binding Ritual.
Chapter 266 of the series sees Nacht bring Asta to a strange house to begin their training, and he reveals that he will be teaching Asta how to bring out the full slate of the Devil's power. The forbidden Devil-Binding Ritual will involve Asta making a contract with his Devil and formally make the power his own.
Completing this ritual successfully will allow Asta to use the power at will, and requires a connection to the Devil. Nacht reveals that he himself uses relics to connect the Devils to him (and thus summon them to the real world), but Asta has no need for those relics. Because of his grimmoire and his new Devil arm (that he sacrificed for a boost of power in the fight against Dante), Asta himself is the relic that connects him to his Devil.
Thus Asta's next phase of training will now see him taking on his own Devil in order to command it properly from here on out. If Asta indeed takes control of his Devil, then it will put him on the same level as the Dark Triad and Nacht, who work together with their Devils on the same level.
But what do you think? Ready to see Asta take on his Devil in the attempt to control? Did you even think it was possible for Asta to have a formal contract with his Devil? How do you think it will change him going forward? Let us know your thoughts in the comments or you can even reach out to me directly about all things animated and other cool stuff @Valdezology on Twitter!