As Think Tank, he was a member of the Resistants, which was originally an incarnation of the Brotherhood of Evil Mutants. The Resistants opposed the Mutant Registration Act. Think-Tank fought Captain America. He was imprisoned, and resumed his Mentallo identity. He started a mass breakout at the Vault by using Venom due to Truman Marsh's treatment. However, his powers were briefly amplified and used by Iron Man to compel the escapees to surrender. He then directed an unsuccessful attack on the Hulk and the Thing. Mentallo later attended the A.I.M. weapons exposition.