Dark Lord of the Sith (Destiny)

The title of Dark Lord of the Sith — or Dark Lady of the Sith — was typically held by a single individual who was recognized as ruler of the Sith. For several thousand years, this mantle was furiously coveted, leading to infighting among the Sith as they warred for claim of the title.

While traditionally there could only be one Dark Lord, this practice was abolished by the reign of, who named all of his followers Dark Lords in the hopes of preventing the same infighting that had torn their ranks apart many times in the past. After Kaan's was destroyed,  implemented this concept into his own, where the title of Dark Lord was held by master and apprentice alike.