Seven Barian Emperors are group of Barians that exist in Yu-Gi-Oh! ZEXAL anime which are originally led by Nasch. They have an agenda's on gathering the Numbers and destroying Astral World taking part of Different-Dimension War. According to Vector, there were originally seven of them, but after Nasch and Mearg disappearance they were left with five and Dumon becoming in control.
Long ago, each of the Seven Barian Emperors had once lived a life as human having a previous life and their legend being inscribed in the seven "Number" ruins. Example, Alito was a utmost warrior to ever exist using just his bare hand in a land that was later to be known as Spartan City, Dumon was a knight who served to protect a kingdom he lived in along with his pegasus, Mizar was a mighty dragon tamer who protected his land alongside his pet dragon, Girag was a great warrior known for being wise and benevolent often sharing the spoils of his conquests with the populace, Vector was a ruthless prince and conqueror of kingdoms, and Nasch and Marin were a prince and princess.
Unknown Years later, all this people were born as Barians with no memories of there past lifes and got together forming "Seven Barian Emperors" group and started plotting a plan to destroy Astral World. At some point, both Nasch and Mearg were murdered by Vector leading with Dumon to lead the group, who believes both simply vanished.