Fear Itself
Nul is one of Cul Borson’s eight children that he transformed into magical hammers when Odin was close to final victory.
When Sin, daughter of the Red Skull, recovered the hammer of Skadi, the sibling hammers fell to Earth near superhumans considered worthy to weild them. Nul, the Breaker of Worlds, fell near an area where Hulk and the Red She-Hulk were trying to reconcile. Like with the other hammers, Nul possesed the Hulk when he touched the hammer.
The first impulse of Nul in his new shape was to get rid of the Red She-Hulk and chased her through a slum village before being summoned to New York to aid his brother Angrir (the Thing) in battling Thor. The ensuring battle saw Thor blast Nul across the world and land him in the heartland of the Vampire Nation. Caring not for who he fought, Nul proceeded to devastate the area and anyone who crossed his path.
In the end the Hulk’s wild nature along with some external coaxing manages to beat Nul back into the hammer before crushing it between his hands. Unknown to them all that doing so allowed Nul to break free, letting him become a problem for the latest incarnation of the Defenders.