When Mammomax first appeared, he was part of the Brotherhood of Mutants alongside Avalanche, Sabretooth, Exodus, Juggernaut, Nocturne, and Black Tom Cassidy. He participated in an attack on the X-Mansion, which caused massive property damage and the deaths of at least two of its residents. Iceman defeated him. The entire Brotherhood ended up sucked into the black hole within Xorn's head, which apparently leads to the Mojoverse. The Brotherhood bargained with Mojo, apparently giving him Juggernaut and Nocturne in price for their freedom.
Mammomax next appears after M-Day, on the run from members of the Sapien League with Erg and Peepers. At the Institute's front gates, the X-Men save him from being burned alive. He took up residence on the Institute's grounds with other members of the 198. He also forms a friendship with Erg, Fever Pitch, and Sack. During an outing into Salem Center, he attacks a boy for calling him "Elephant Man", but a "tracking chip", implanted in his head by the Office of National Emergency, disables him before he could do any damage. Mammomax has the device removed by Mr. M. The other members of the 198 also have their chips neutralized. Mammomax follows Mr. M during his exodus from the Xavier Institute.
Mammomax was later captured by the Facility, the same group responsible for the creation of X-23. He is used as a test subject for Predator-X created by the Facility staff. Predator X consumes and kills him. A picture of his corpse is shown to Mercury, who had also been taken by the organization.
Powers and Abilities
Superhuman Strength: Mammomax was superhumanly strong and, at his peak, possessed sufficient superhuman strength to lift up to 20 tons.
Superhuman Durability: Mammomax possessed a tough, elephant-like skin, muscle and bone tissues that rendered him highly resistant to conventional physical injury. Mammomax could withstand tremendous impact forces, high caliber bullts, falls from great heights, powerful energy blasts, attackes from most bladed weapons and exposure to temperature extremes without sustaining injury.
Corrosive Expulsion: Mammomax also possessed the ability to expel highly corrosive stomach acid from his mouth. While he himself was immune to the corrosive effects, the acid was able to dissolve and eat through most conventional materials.
Mammomax possessed sufficient superhuman strength to lift 20 tons.