WARNING: The following contains spoilers for Fantastic Four #41, now on sale from Marvel Comics
The current conflict enveloping the Marvel Universe -- the Reckoning War -- has quickly escalated beyond to a crisis level event. To save the universe, they'll have to resort to some very drastic ideas, such as turning one of Marvel's most powerful forces into a cosmic battering ram.
Fantastic Four #41 by Dan Slott, Rachael Stott, Erick Arciniega, and VC's Joe Caramagna fuses Galactus with the Asgardian weapon known as the Destroyer (who made his Marvel Cinematic Universe debut in Thor) -- effectively turning Galactus into an uncontrollable weapon and proving just how dangerous Galactus can be as a tool of pure destruction.
The Reckoning War has already been a monumental challenge for the heroes of the Marvel Universe, with the destruction of the moon only starting the cosmic conflict. To deal with the horde of powerhouse alien warriors emboldened by the Reckoning's return, the heroes have been forced to make some difficult choices -- such as Reed Richards embracing a potentially lethal amount of knowledge to figure out a way to save all of creation. But the heroes gain an unexpected -- and radically dangerous -- edge thanks to the Silver Surfer and Thor. Galactus is currently dead by Thor's hand, with his skull serving as part of the gate to Asgard. But amidst the chaos consuming the galaxy, Thor discovers the former heralds of Galactus trying to empower the body to resurrect the cosmic entity.
Thor is shocked that the Destroyer armor also sees the Galactus as essential to the universe. Walking into the field, the Destroyer merges with Galactus, giving the cosmic force new life as "the Destruction." It's a radically powerful and likely uncontrollable form for Galactus, and one the heroes can use to their advantage. Using his own Power Cosmic, the Silver Surfer is able to use the energies of the Ultimate Nullifier to lead the Destruction away from Asgard -- with his express plan being to lead it directly into the path of the Reckoning's army, where it can ideally do some serious damage to their forces and help rescue the wounded Eternity.
It's a wild plan, but not the first time a Marvel character has transformed the cosmic entity into a weapon. Annihilus captured Galactus and the Surfer to use as engines for his war machine in Annihilation. A notably powerful variant of Kang the Conqueror once fused himself with Galactus, giving him access to the Power Cosmic, and aspects of his technology have been turned into planet-cleansing tools in books like Guardians of the Galaxy. None of that even compares to what he can do when he's actively trying to help destroy something either -- the sheer power of Galactus is enough to make entire empires shake in fear, and his need to consume obscene amounts of energy to continue his cosmic duty means entire planets can easily fall before him.
Galactus has even faced off with other cosmic entities before (such as in the battle against the Mad Celestials during Jonathan Hickman's FF run or against the denizens of the Cancerverse in The Thanos Imperative), using his sheer power as the equivalent of a cosmic wrecking ball against the more specific strategies of other cosmic forces. Especially when turned into a weapon -- such as his current form as the Destruction -- Galactus might be one of the most potent tools of destruction in the Marvel multiverse. Just leading the Destruction into the Reckoning's army will likely lay waste to their forces -- and in turn allow Galactus to actually help save the universe before inevitably restoring the famed world-ender to a form more akin to his classic incarnation.