Teiōgan

The is the powerful  kekkei genkai utilized by the Abura Clan. While its progenitor was Abura Uchiha, who first used the eye, it was a direct result of the genetics of Fūjin Uchiha's Rinnegan and Yūgao Hyūga's Byakugan. The eyes themselves then manifested in Abura Uchiha, who would lend her genetics and her name to her descendants, who would become the Abura clan. The Teiōgan has also been called the because of its heritage and connection with the ancient Rinnegan.

Background
The Teiōgan is a rather recent mutation, having appeared 300 years before the start of the series in Abura Uchiha — the daughter of Fūjin Uchiha and Yūgao Hyūga. Having received the genes for all three of the Three Great Dōjutsu, Abura's eyes mutated and became the Teiōgan. After brought the  down upon the earth, wiping out a tremendous majority of humanity, Abura survived and continued her lineage, which took her name and became the Abura clan.

Similarly to Abura, Echo Uchiha — a time-traveling member of the clan and a self-professed descendant of Ryun Uchiha — also awakened the Teiōgan, though his possessed a tomoe design, leading to the name.

Abilities
The Teiōgan, like its parental dōjutsu, gives the user extraordinary perception. It gives color to chakra, allowing the user to see it, and also gives the user enough sight to see the Eight Gates within the human body. The eye can easily dispel genjutsu, making it virtually impossible to capture users with illusions. The Teiōgan also retains the Sharingan's capability to track extremely fast movement, though it has lost the ability to copy ninjutsu. Conversely, unlike the Sharingan, and much more like the Byakugan, the Teiōgan does not evolve into various stages: instead remaining in the same form throughout the user's life.

Unlike the Sharingan and Byakugan (and some incarnations of the Rinnegan, the Teiōgan, once activated, does not deactivate. For this reason, it can be speculated that the eye costs the user little to no chakra. This does not hold true, however, for those who have a transplanted Teiōgan — as they are often unable to handle the chakra drain caused by merely one of the eyes, much less a complete pair. From this, it can be inferred that members of the Abura clan have bodies adapted to the drain of the Teiōgan, whereas others do not.

Receiving the Teiōgan
Like the Byakugan, the Teiōgan is a dominant trait, inherent in every member of the Abura clan from birth. It "awakens" when the user is old enough to mold and develop their own chakra and is in a state of activation from then on.

It is also possible to transplant the Teiōgan into a non-Abura clan host body, however, doing so is extremely dangerous. The chakra drain in a non-Abura clan member, who does not have a significant level of chakra control and development, can lead to an expedited death. Even for those who are conditioned to the vast consumption of chakra cannot use even one for extended periods of time, and two is unheard of. This usually requires the transplant patient to cover the eye, when not in use, to conserve their chakra. It can also mean prolonged periods of recovery after using it in combat.

Demon Sharingan
A time-traveler, Echo Uchiha came to the past to fight alongside his grandfather, Ryun Uchiha, against numerous threats: eventually becoming a member of the Yonkō. Like Abura (Ryun's granddaughter), Echo awakened a unique, green dōjutsu rather than a normal Sharingan. Due to a lack of a better name, Echo referred to his eyes as the — stemming from the belief that the eyes were a result of a curse implemented by his mother. Indeed his eyes, originally a Teiōgan, evolved due to an unknown stimulus, into a mutation of the Sharingan: a trait which allowed it to eventually evolve into a.

Trivia

 * "Teiō" (帝王) can also refer to an.