The Xorn brothers' mutant natures manifested as tiny stars inside their heads that flared out of control, devastating their small village in China until villagers managed to clamp metal masks around what was left of their heads. The anti-mutant Communist regime separated the brothers, keeping Shen in isolation in the village while Kuan-Yin was incarcerated in an underground prison. Kuan-Yin escaped once, but was recaptured soon after and a new prison constructed around him. Meanwhile, the Chinese government formed the Eight Immortals to keep Shen secure. Later, Kuan-Yin's warden made a deal to sell him to John Sublime, who sought to harvest Kuan-Yin's mutant mind. Rather than face such a grisly fate, Kuan-Yin attempted suicide by reversing the power of his star, creating a black hole that threatened to destroy the world. The X-Men arrived to defuse the situation by inviting Kuan-Yin to join the team. He accepted, but first sought time to meditate.
Cyclops later visited Kuan-Yin to seek help against the threat of Nano-Sentinels released by the malevolent Cassandra Nova. They were captured by the alien Shi'ar's Imperial Guard, which had fallen under Nova's control, but managed to escape to the Xavier Institute where Kuan-Yin healed the X-Men, allowing them to better oppose Nova. Kuan-Yin subsequently took up a teaching position at the Institute and came to instruct the Special Class, into which he unsuccessfully attempted to recruit the powerful young mutant Carter Ghazikhanian. At some point, Kuan-Yin was coerced by an unknown party into believing he was the X-Men's nemesis Magneto, and he launched a devastating attack on Manhattan which was opposed by the X-Men. Kuan-Yin killed Jean Grey and was subsequently slain by Wolverine.
Later, the X-Men were called to China after Shen's powers had again flared out of control. Opposed by the Eight Immortals, the Chinese Army, and Chinese national hero the Collective Man, the X-Men prevailed. After taking Shen to the Institute, he sensed that the individual responsible for his brother's corruption had been hiding amongst the X-Men for some time, and was still in their midst. Shen subsequently joined the X-Men in opposing an attack by the Brotherhood of Mutants. To stop the killing, Shen saw no alternative but to release his black hole, pulling the villains into the void. He then left the X-Men to reflect on the immensity of his actions.
After the events of House_of_M|M-Day, Xorn's consciousness took control of the collected energies of the Earth's depowered mutants and attempted to bond with the Magneto, in exile in Genosha. The Sentry forced the collective into the sun, seemingly ridding the world of Xorn once and for all.