As one of his dimension's Master of the Mental Arts, Yandroth attained the power of Scientist supreme, becoming dictator of the planet Yann and others. When the Earth woman Victoria Bentley was displaced into Yandroth's dimension during a clash between Nebulos and the Living Tribunal, Yandroth hoped to enslave her, but Dr. Strange (Stephen Strange) intervened, defeating Yandroth and the robot Voltorg. When Yandroth teleported away, Strange redirected him into the "Dimension of Dreams" and their renewed battle left Yandroth falling through interconnected dimensions. In Yandroth's absence Dr. Christopher Ganyrog became Scientist Supreme.
Developing enough mystic ability to reach Earth, Yandroth used both science and magic to create Omegatron, an artificial intelligence capable of detonating Earth's nuclear stockpiles; Yandroth intended to channel the energies of Earth's destruction and, following his physical death, be reborn in his own dimension with a new omnipotent body. Yandroth mocked Strange with his knowledge before succumbing to self-inflicted death, but Strange, newly allied with the Hulk and the Sub-Mariner as the Defenders, prevented Omegatran's full activation. Unable to destroy Yandroth's creation, Strange cast a time-manipulating spell to prevent it from reaching activation point. Days later, Omegatron reactivated when Strange's spell weakened, even assuming gigantic humanoid form, but Defenders Hulk (Bruce Banner), Sub-Mariner, Valkyrie and their ally Namorita again deactivated it.
Due to his Yannian nature, Yandroth survived in astral form. Eventually he took possession of the chemist Stephanie Doral, whose brain patterns chanced to be identical to his own, but she overwhelmed his consciousness and, using his genius to build advance weaponry, mentally controlled Defenders Hulk, Nighthawk, Valkyrie, Hellcat and Clea. Strange manipulated her into overtaxing her new powers, and Yandroth's psyche was driven out. Days later, veterinarian Jeff Colt became linked to Omegatron and obtained superhuman powers, inadvertently threatening to fully activate it, but Strange served his connection and restored Omegatron to inertness.
Years later, his astral form nearly dissipating, Yandroth possessed a near-dead homeless man. Unaware of his identity, Hellcat helped restore him to health, but Yandroth, transforming his new body into a duplicate of his own, abducting her, then captured Earth goddess Gaea, whose power he used to unleash various threats throughout Earth, including Gorgilla, Night-Crawler, Quasimodo, Warlord Kaa and his followers, Borers, Gargoyles, Living Erasers, Lizard Men, Mindless Ones, Tribbitites and more; as Earth's super-humans battled the intruders, Yandroth absorbed their powers. Hellcat escaped and with Nighthawk's help, summoned Doctor Strange, the Hulk, Sub-Mariner and the Silver Surfer to confront Yandroth. He then summoned the Ravagers of Creation, four entities capable of destroying the Earth and providing power to the powerless Omegatron, but the gathered Defenders drove the Ravagers away. Again dying, Yandroth used Gaea's power to curse the quarrelsome four to forcibly gather whenever Earth faced severe danger. The four Defenders battled such threats until Yandroth's curse corrupted them into attempting to takeover the Earth as the Order, and they fought many fellow super-heroes. Meanwhile, Yandroth, again an astral form, channeled energies into his own dimension, wreaking havoc on Yann and hoping to destroy it and use its as he had intended to use Earth's; however, Yandroth manifested his new body too soon, and when the Defenders came to their senses and ceased hostilities, the energy cessation reverted him to his original humanoid form. Yann's authorities then arrested him.