WARNING: The following contains spoilers for Black Clover Chapter 289, “Freezing Sun,” by Yuki Tabata, Taylor Engel and Annaliese "Ace" Christman, available now in English from Viz Media.
All the greats of shonen have fallen victim to time running out on their ultimate transformations, and now Asta and Liebe face the same fate in Black Clover Chapter #290, “The Highest vs. the Lowest.” With his new form running out the clock, it seems Asta has wasted too much time away from the actual threat, the Dark Triad. After sacrificing his greatest advantage to save Nacht, the master plan to stop the devils will have to take a detour. Knowing Nacht, he won’t be too happy about Asta’s decision to save him, but Asta and Liebe might have other skills up their sleeves yet.
Lilith and Naamah prove too powerful for any human mage currently on the battlefield, so Asta’s new form was necessary to defeat the hybrid devil. Although the form is spent, Asta still has his anti-magic. His and Liebe's creativity will be needed to stall long enough to come up with an advantage against the Dark Traid. Also, recharge time on Asta and Liebe's Devil Union is still unknown but, with Asta’s dependability in dire situations, he’s probably aware of his own limits and knows that he and Liebe could transform again if there's no other choice.
Regardless of Asta’s limits, he'll still need time to build his strength for another Devil Union. Thankfully, the pair have the other Magic Knights, especially the approaching Black Bulls, to back them up. Asta and Liebe will likely need protection as they rest up, which will put many Magic Knights in danger. The mages are up against devils, whose strength is still rising to levels unheard of in the human world. Every minute counts, even without Asta and Liebe’s timed Union.
On top of that, the Dark Triad still has the upper hand in the current situation. The Magic Captains that were supposed to be facing off against them are no longer in play, and their ultimate ace is currently out of juice. Nacht’s plan to stop the devils is slowly crumbling, and all hope seems lost -- especially once Lucifero manifests in the human world with his real body. The moment the Dark Triad loses their devil counterparts will be when the tide of battle permanently shifts, since the Spade Kingdom will likely lose their tyrants, the Zogratis, and give rise to the world’s newest threat, Lucifero.
A key part of Nacht’s plan was destroying the ritual of Qliphoth and, despite how things are going, there might still be time to stop it. Yami and Vengeance are being held captive as fuel for the ritual, so freeing them is clearly the best way to disrupt it. But, the longer things take, the more time there is for the devils to emerge at full strength. If the ritual is stopped in time, though, Nacht's plan could still pan out. The Black Bulls were likely tasked with freeing Yami and Vengeance, and since they're surprisingly laid-back while en route to battle, they may have already done it.
With all the chaos, Asta losing his union with Liebe could be the best decoy needed to stop the overall problem: the manifestation of all devils. Asta’s anti-magic was always his greatest strength, but now his vulnerability could create humanity's best opening to strike back against the devils. The devils have now gotten a taste of Asta and Liebe’s union and will likely try to avoid another confrontation with it. Both the devils and humans are going to be battling against the clock, making time the ultimate hurdle in the current battle. The side that makes the best use of it will gain the upper hand.