The Geass is a mysterious ability which a species of immortal-humans can bestow upon others. The power is always present in the eyes, but the manifestation of the Geass is dependent the user's will.
The Geass (ギアス, giasu) is a mystical ability that was introduced in the anime series Code Geass: Lelouch of the Rebellion(LotR). The series creators are the series director, Goro Taniguchi; and the writer, Ichirou Ohkouchi. It's also sometimes referred to as the Power of Kings (王の力 , Ō no Chikara), and that all who use it are destined for loneliness. The name is derived from a magical form of contract in Irish mythology called a "geas" or "geis".
Known Geass Users
In the Code Geass: LotR series, it was initially believed that Lelouch was the only wielder of the Geass power. A second Geass user was introduced in season one, and by season two. Several more were revealed to of had the Geass long before Lelouch.