Y'Garon is a demon who has clashed with Marada the She-Wolf and Dracula.

Yandroth was the humanoid Scientist Supreme of the "otherdimensional" planet "Yann" and a would-be-conqueror who, with his robot Voltorg, has fought Doctor Strange as a counterpart to the latter's title of Sorcerer Supreme. Doctor Strange defeats Yandroth, sending him to seemingly fall forever through an alternate dimension, the Dimension of Dreams.

There, he gains great magical knowledge and learns that he could gain great power by destroying a world. He returns to Earth and constructs an "Omegatron", although he suffers injuries received when he was hit by a truck in New York City. His physical body dies, thus activating the Omegatron. As the Omegatron, he battles Doctor Strange, Namor, and the Hulk, who come together as the Defenders for the first time. Yandroth is placed under a time displacement spell by Doctor Strange.

The Omegatron is eventually released from the time displacement spell and battled Namor, the Hulk, Valkyrie, and Namorita and was destroyed. Yandroth's spirit next possesses a young female chemist to telepathically attack the heroes; however, he is defeated by the Defenders again.

Although Yandroth is dead, his spirit is still capable of taking possession of a living human's mind. Taking the form of a vagrant, he is discovered by Patsy Walker. Seemingly an innocent, she rescues him, allowing him to regain his strength and capture her. He becomes a nihilist and crafts a plan to end the world. He summons monsters from all over like Negative Zone Borers, Mindless Ones, Toad Men, Dark-Crawler, Quasimodo, Warlord Kaa and his Shadow Warriors, Living Erasers, Gorgilla, Vi-Locks, and the Lizard Men of Tok. This attack involved many superhero teams. Most of the New York-based heroes are tied up confronting destructive, mindless monstrosities. Alpha Flight is attacked by Warlord Kaa and his Shadow Warriors. Yandroth causes a group of Living Erasers to appear in the Tokyo Headquarters of Big Hero 6. The Lizard Men from Tok attack the island nation of Genosha. Gorgilla subdues the Avengers by dropping a building on them. It turns out he is utilizing the captured form of Gaea, the spirit of the Earth, to summon the monsters. Patsy, who had escaped and learned this, tells the Defenders, who were currently comprising Namor, Hulk, Doctor Strange, and Silver Surfer. The superheroes battles Yandroth has caused has given him enough power to summon the Ravagers of Creation. Four elemental creatures confront the Defenders, who are unable to stop them individually. They attack the Stone creature, disabling the spell needed to destroy the world. This frees Gaea and kills Yandroth. In his dying breath as the Hulk and Namor fight, he realizes the Defenders hate each other. Yandroth uses his powers to curse the four original members so that they must come and work together in times of a severe crisis. This involves uncontrollable teleportation, affecting all four of the heroes. Yandroth's curse caused the Defenders to work together against a plot by Lorelei and Pluto. The curse that Yandroth placed on the four original members of the Defenders was also tied to Yann and adding into Yandroth's powers.

When the four Defenders members became The Order for a short time, their curse started to cause Yandroth to slowly reform. He started to slowly materialize in smoky form above a throne. Yandroth then began to materialize in an all-powerful mist-like form. When he was denied of the final power he needed when the Order wouldn't attack him, Yandroth regressed to human form as Christopher Ganyrog took Yandroth back to Yann to stand trial for his crimes.

Yandroth is featured in the limited series "The Last Defenders", disguised as a businessman after he escaped, killed the Ganyrogs, and took over Yann. Assisted by the floating head of the entity known as the "Recorder", he attempts to manipulate his way into gaining god-level powers. Nighthawk, Colossus, Blazing Skull She-Hulk, and Warlord Krang battle the group the Sons of the Serpent which culminates in a confrontation with Yandroth. Yandroth manipulates time and forces Nighthawk to battle a twisted version of his old team the Squadron Sinister before being rescued by a future incarnation of the Defenders, who with Yandroth disappear once the threat is over.

This Yeti, an Inhuman mutated by the Terrigen Mist, was created by Stan Lee and Jack Kirby and first appeared in Fantastic Four #99.