Tengen

Tengen (天元), often referred to as Master Tengen (天元様) is a recurring character in Jujutsu Kaisen that has yet to physically appear in the series. They are an immortal jujutsu sorcerer that remains within their chamber: the Tombs of the Star Corridor at all times in order to reinforce the barriers that protect both Jujutsu High locations.

Master Tengen is also known as the "Star" (星). They are responsible for preaching the foundation of jujutsu sorcerers and spawning religious groups that worship the Star as their deity.

Appearance and Personality
Presently Master Tengen has not appeared physically in the story and has only been referred to by other characters.

History
During the Nara Period, Master Tengen spread Japanese Buddhism and preached what would become the foundation for jujutsu sorcerers.

Gojo's Past Arc
In the modern age Master Tegen does not interact with the outside world. They use a barrier technique to protect both jujutsu schools and to strengthen all of the auxiliary managers barrier techniques. Their immortality cursed technique must be reset once their body reaches a certain age. The technique will attempt to change bodies, forcibly evolving Tengen to a higher state, losing their will and potentially making them an enemy to humanity.

In order to prevent this, every five hundred years Master Tengen must merge with a compatible star plasma vessel to rewrite their body's information. Once the body is refreshed, the cursed technique will be reset as well. In 2006, the Star Plasma Vessel was Riko Amanai.

Two groups targeted the girl; the curse user group Q who aimed to overturn the jujutsu world by having Tengen lose all reason, and the Time Vessel Association, the star religious group that worshipped Tengen as their deity. In order to ensure Riko's safety, Master Tengen had Masamichi Yaga assign his students Satoru Gojo and Suguru Geto with escorting the girl to Jujutsu High before the merger on the full moon.

Riko is ultimately assassinated by Toji Fushiguro who was contracted by the Time Vessel Association to kill the girl and prevent the impure merger. Even so, Master Tengen was somehow able to stabilize according to Yuki Tsukumo.

Abilities
Overall Skill Level: While Tengen does not interact with the outside world or go on missions, their abilities have been essential to protecting the pillars of the jujutsu world for thousands of years.