He attacks an asteroid within the Dark Nebula with the intention of harnessing the power of Xorr the God-Jewel. However, he finds Thor and the Asgardians there before him, and instigates battle. While fighting personally with Thor, Mercurio tells him of how he survived their last encounter - having been thrown to another level of space - and tells him of his discovery of the God-Jewel and the power it holds. Suddenly, the jewel rises out of the asteroid and warns them all to stay back under threat of destruction.

He listens to Xorr's warnings and can do naught to attack. He is plunged into a cavern and forms a temporary alliance with Thor and his band to allow them all to escape. They battle the now hypnotised miners and reach the surface, but a spaceship piloted by the lead miners has taken hold of the God-Jewel and is flying away. They pursue the ship, and Thor destroys their weaponry with Mjolnir, allowing the Asgardians to eventually catch up. Mercurio is beaten back by Kagg's molecular disruptor, which Odin is able to destroy, but Thor refuses to destroy the God-Jewel and Xorr remains empowered.

He ignores Thor's warnings to stay back and tries to attack Xorr anyway. Thor beats him back and he retreats. Mercurio soon returns with more Gramosian forces and renews battle with Thor. As Mercurio begins to lose, however, he seeks an alternative when he spies Xorr trying to harness the energy of a star going supernova. He allies with Thor and they free Sif and Karnilla, and the Gramosians gather the remainders of the God-Jewel to save their planet.