Before his transformation, Mammoth was a lean, pale teenager with shocking red hair. He wore a blue tank top that exposed his abdomen and a black collar. After the transformation, his skin was changed to a greenish-brown color, but he kept his red hair. His teeth became pointed. As a result of his treatment, his skin cracked in places, exposing red muscles underneath. He wore black shorts after he was transformed.
Mammoth was Kobra's champion. When the Kobra-Venom was first produced, he was injected with one ampule of the drug by his twin sisterShimmer. He was permanently transformed into a super strong monstrosity. The muscle enhancement gained from his transformation was so great that it actually split and separated his newly hardened skin. He easily defeated Bane in one-on-one combat.
Mammoth broke into the Gotham City Observatory to kidnap Jason Burr for his master Kobra. Batman and Robin tried to intervene, but Mammoth was too strong. He dropped one of the orrery's planets on Batman, pinning him down, and knocked out Robin when he tried to sneak up on him from behind.
Batman, Flash and Green Arrow and their protégés interfered with the ritual, forcing Mammoth to engage them. He outmatched both Batman and Flash, but couldn't finish them as his master had by now completed the ritual, and Mammoth needed to worship him. Because the elder heroes left to stop a giant cobra from tearing through downtown Minneapolis, Mammoth was left with their sidekicks. Kid Flash defeated him by throwing a sleeping gas pellet in his mouth. He was sent to Belle Reve Penitentiary.
At Belle Reve, he worked as muscle and body guard to higher ranking prisoners (specifically Icicle Sr.). He later participated in a mass breakout attempt by helping Blockbuster break down walls that had been weakened by freezing them. Mister Freeze later took him and Blockbuster to confront Icicle Jr., who had reactivated the inhibitor collars. Junior froze him.
The Justice League, Superboy, Miss Martian's valiant effort against Kylstar convinced him to treat his sentient weapons better. All captives, including Mammoth, were released, and Orb-One explained Kylstar's motives. He was a freedom fighter who was on a mission to stop slavers who destroyed his homeworld. As a sign of his good intentions, he offered to return captives unwilling to help with his fight back to their homeworlds. Those willing to stay were promised good treatment and glorious battle.
The Collector's Ship December 1, 19:01EST
Mammoth, along with all of Kylstar's captives from Earth, were teleported into the Collector's Ship. With the additional reinforcements, the Collector's body was quickly destroyed.
Metropolis December 1, 19:03EST
The body was merely one of many, and the Collector unleashed several additional Coludroids on the assembly. The battle was interrupted when the Collector noticed that the probe he embedded underneath Metropolis was malfunctioning. If nothing was done, Earth would be destroyed. Since the Collector was a preserver and not a destroyer, he agreed to shut off the beam that was slowly shrinking the City. After the assembled heroes convince him of their determination to prevent him from taking the city, he begrudgingly agreed to resize it back to normal and leave.
Metropolis December 1, 22:03EST
The Collector teleported all Earthlings into the city. The villains were nowhere in sight, and the assembled heroes thought that the Collector had teleported them elsewhere to spite them. Unbeknownst to them, the villains were actually just yards away, mentally shielded by Gorilla Grodd, who informed them they now owed him.
Soon after they arrived in their main base of operations, intruders were spotted.
Batgirl was captured and stored with the other runaways, and Psimon sent Mammoth and Devastation to load them all aboard a plane that was standing by. With that done, Psimon noticed Miss Martian had impersonated Shimmer. Mammoth was angry that his sister was hurt, and they would kill Miss Martian while she was in battle with Psimon. Because Bumblebee had freed Batgirl and they had started the plane, Mammoth was sent after the plane instead. His first attack was beaten back, but he threw a forklift at the plane, which destroyed one of its wings. Nonetheless, the plane got away.
Bialya February 20, post-10:34UTC+2
Mammoth had taken his sister out of the drum, but she was still unconscious when Queen Bee checked on the damage in person.
Mammoth, Shimmer and Devastation made a show of defending the Bialyan temple base against a joint Team-League incursion. A combination of Batgirl's martial arts and Zatanna's magic sent them all through a hole in the floor created by Shimmer.
In the comics, Mammoth and Shimmer are Teen Titans villains, often associated with the Fearsome Five. This is his second animated appearance; he was a member of H.I.V.E. in the Teen Titans TV series, voiced by Kevin Michael Richardson.