Doomquest is an alien warlord who appears in the final episode of the ninth season of the 1987-1996 series, entitled Doomquest. He is originally from from a dimensional world called the Dark Realm, and his ultimate goal is to merge the Earth's dimension with his own.
To this end, he spent centuries seeking the Vortex Crystal, a powerful object that can warp space and destroy dimensional barriers. Shortly after Lord Dregg obtained the crystal, Doomquest appeared on Earth to take it from him, capturing Dregg's ship and sending his servant Draconus to take the crystal back from the Turtles.
Once Draconus had brought him the crystal, Doomquest began dissolving the dimensional barriers between the two dimensions, allowing monsters to roam through the city. When the Turtles arrived to take the crystal from him, Doomquest proved to be a formidable foe, but was distracted by an attack by the Dreggnaught. When Leonardo smashed the crystal against Doomquest's ship, Doomquest was sucked into the Dark Realm along with his forces.
Powers and abilities
Doomquest is one of the most powerful beings in the entire series, possessing an unimaginable level of strength - enough to easily shake off and knock back two of the Turtles in their super mutated forms with one arm, both of which are strong enough to level and shatter a dam.
Doomquest can also fire very powerful lasers from his eyes and fingers/hands, and could charge matter which can be seen when he picks up a rock and energizes it. Doomquest has fought off and overpowered the Dreggnaught, which can destroy a planet as seen in the episode, The Day the Earth Disappeared.