Dementoid is a green-skinned "rehabilitating" criminal who joined the Redeemers in taking down the Sinister Spider-Man, Venom (Mac Gargan).
Once, while committing a robbery, Spider-Man attacked him, and Dementoid's powers had no affect. Spider-Man than secretly ate both his arms. This was a problem, but not as bad as some of the other Redeemer's injuries since Dementoid at least had two tentacles. The Redeemer then convinced him to join the Redeemers.
When the Redeemers tried to make Spider-Man apologize for his crimes, take therapy, and perform community service, Venom refused. In the ensuing battle Dementoid was beaten and defeated but did not die or lose any more limbs (although the symbiote did grow a mouth over Gargan's sphincter that did nearly kill him) Spider-Man let him get away rather than have him tell his story to anyone. The Dementoid was with the other two Redeemers not incarcerated or killed (Redeemer and General Wolfram). When the Redeemer announced another plan to "redeem" Spider-Man, Dementoid was reluctant. However, he later agreed and the trio sent images of Spider-Man doing various horrible crimes to Mayor J. Jonah Jameson.
Powers and Abilities
The Dementoid is able to drive most people insane by his touch, but for some reason this did not work on the Sinister Spiderman (possibly because of the alien symbiote and/or Gargan was already insane). He has two cyborg arms that function reasonably well; it is unknown if they have any superhuman abilities. He also possesses two tentacles. His appearance is green, bald, tall, and distorted though his origin is unknown.