Kurobyougan

The Kurobyougan is said to be one of the most powerful {{nw|kekkei genkai]] in existence, in par, if not more powerful, than that of the Rinnegan;

The Kurobyougan changes color and shape depending on the user's personality and a change, For example, Blue means a calm and shy person, that will turn into insanity, Or red, That means a loving and caring person, that will change into hatred and violence;

The only way to awaken the Kurobyougan is losing one of the people closest to you, and the main way to evolve it and evade the personality change is to Kill all you most love, something similar to that of the Mangekyō Sharingan; the other way to evolve the Kurobyougan is to obtain a fully mature and unique Rinnegan and obtain a large part of the elemental Kekkei Genkai.

(This would explain why Heiro is obsessed with obtaining the final version of the Rinnegan and obtaining the Kekkei Genkei, refering to "Paradise" as a sane state of mind, however, when the Kurobyougan first version awakens, the changes you go into transform you into a nonthinking beast, it is possible that Heiro really means destroying the shinobi nations, or he found a way to counter the Eye's sickness)

The Kurobyougan normally propagates on members of the Azure clan, the eyes would normally attain a Cerulean color, similar of that of the clan's name, but it is not exclusive to the Azure clan, i can propagate into Uchiha (Red), Senju (Green), Hyuuga (Purple), Uzumaki (Orange) and the Kaguya (Yellow);

Two Kurobyougan's cannot exist at the same time, The whole pair of one person must be destroyed before another is born, The destruction of konohagakure no sato during the Fourth great ninja war destroyed the hidden eye that kept any new ones from being generated (That one being an orange Version) and that later on propagated to Heiro, Who now has the last pair of eyes until he dies and another one unlocks it.

Abilities
The Kurobyougan's full ability set are unknown; What is known about them is that:


 * They Give the user a great control over Chakra, making their control even better than a Rinnegan would


 * Their elemental affinity(es) are improved dramatically, making one able to control certain elements with only their toughts


 * One can absorb Bloodlines from another, Like The Sharingan or Mokuton for example, The victim must die, but the wielder will receive the bloodline; But any offspring of said wielder will receive only one or two Bloodline limits


 * It has abilities similar to that of the Rinnegan, Sharingan and Byakugan, (it is possible that the Dojutsu mentioned were descended from the Kurobyougan, As were all the Kekkei Genkai)


 * One can divide their bodies in ten parts, Similar to that of Six Paths of Pain and the Jiongu Hearts.

Those abilities may vary from one wielder and another, and there may be thousands of techniques we don't know yet.