He fought Duncan in the pact

Doc Seismic was a mid-level villian with a lackluster career. At times his confrontations seemed heavily ego based, Seismic taking perverse pleasure in the fame and power of the heroes he fought. While carrying out a scheme to destroy Mount Rushmore, Seismic was challenged by Invincible. During the conflict, Doc Seismic fought hard to keep from being defeated by the still unknown hero, causing both combatants to plunge into a crevasse. Invincible attempted to grab Doc Seismic and keep him from falling to his death, but death was more favorable to him than defeat at the hands of an "unknown". In a final act of defiance, Seismic let loose with a shockwave that forced Invincible away before he could rescue the villian. While it was presumed that Doc Seismic was killed by the fall into the crevasse, some months later, Invincible and three other young heroes (ShadowHawk, Firereather, Zephyr) discovered him deep within the Earth while they were investigating an attack by by a group of lava monsters. These monsters were the Magmanites, who now served under the thrall of Doc Seismic. Once Seismic saw Invincible, rather than attacking him, he thanked him for allowing him to thrive in his new underground kingdom. Invincible, however, knocked Seismic out with a sucker punch and took him to prison. Seismic bid his time in jail but later escaped aided by legions of his Magmanite minions, while simultaneously releasing a large number of superpowered inmates. The Guardians of the Globe were unable to prevent his escape but he was recaptured almost immediately with the assistance of Shapesmith.