Tengen

Tengen (also called Master Tengen or simply the "Star") is an ancient, immortal jujutsu sorcerer in Jujutsu Kaisen.

They've existed for over a thousand years (since the Nara period), originally a human who helped spread teachings that became the foundation of jujutsu sorcery. Tengen possesses the innate cursed technique of Immortality, which prevents death but causes their body to evolve over time if not periodically merged with a compatible human vessel (known as a Star Plasma Vessel) every ~500 years.

Due to a past event preventing a merger, Tengen has evolved beyond a normal human form into a more curse-like appearance: a pale, hairless, bipedal humanoid with a cylindrical head and four white eyes, usually wearing a simple robe.

Tengen remains secluded in the Tombs of the Star Corridor (a hidden chamber under Jujutsu High) and serves as a crucial pillar of the jujutsu world by constantly reinforcing powerful protective barriers that safeguard Jujutsu High locations, conceal them from non-sorcerers, and help maintain the stability of jujutsu society overall.