The Ultimate Nullifier is a device of immense power in just about every universe. The Nullifier appears as a small, hand-held metallic device with no apparent functionality. When first introduced in 1966 it was described as the only known weapon in the universe capable of inspiring fear in Galactus.
When Symbiote Galactus destroyed realities in the events of the The Mysterious Five Project, Silver Surfer, Dexter, and Tony Stark used three of them to fend him off from destroying the prime reality.
The Ultimate Nullifier has been described as "the universe's most devastating weapon." As such, the Ultimate Nullifier has the ability to completely eliminate any target the wielder chooses, along with the user if his or her mind is not focused enough. In the hands of a being with an extremely powerful mind, the Ultimate Nullifier can destroy (or in conjunction recreate) entire time-lines from beginning to end.