D'Ken Neramani is a member of the royal family of the Shi'ar Empire, which is governed by the extraterrestrial Shi'ar race and controls all known inhabited planets in their galaxy from Chandilar, the Imperial Throneworld. When his eldest sister, Al'svee, later known as Deathbird, murdering their father presumably to gain the throne, she was exiled instead, placing D'ken in the position of emperor (Majestror). Unfortunately, D'ken was insane.
Once, a Shi'ar scouting ship, on D'ken's orders to collect specimens, was responsible for abducting Christopher Summers and his wife, forcing them to abandon their sons. Summers escaped to become the Starjammers' Corsair, but his wife was used by D'ken for his own pleasure. She was killed before Corsair's very eyes when he finally confronted D'ken, but not before D'ken took his baby from her womb. The child, Gabriel Summers, was artificially aged and given to Eric the Red to be one of his agents on Earth. (D'ken has also been rumored to have fathered another illegitamate child, Adam-X.)
D'ken coveted the power of the M'kraan Crystal, called the "Crystal Heart of Reality," to use as the ultimate weapon. His sister, Lilandra, tried to stop him and was branded a traitor, joining with the Starjammers. Narrowly escaping death, she traveled to Earth and enlisted Professor X and the X-Men's aid, despite the efforts of D'ken and his agents (most notably Eric the Red) to thwart this outcome.
D'ken led the Imperial Guard to the Crystal's location, but the X-Men's Phoenix (the Phoenix Force in the form of Jean Grey) transported the X-Men there to oppose him. D'ken, the Imperial Guard, the X-Men, and the space pirates Starjammers were all transported to a world within the Cyrstal, and the battle threatened to destroy all reality if it were not for the saving power of the Phoenix. D'ken was left incurably insane and nearly catatonic as a result of a pyschic attack on him within the Crystal. Once everyone returned to reality, the X-Men traveled back to Earth, and Lilandra took D'ken's place as empress of the Shi'ar Galaxy.
Garbriel Summers had since become a hero known as Vulcan, although he seemingly perished in his first mission as an X-Men and all information about him and his team was expunged. Reviving after the Scarlet Witch had re-structured reality, he remembered the truth of his parentage and swore revenge on D'ken. He commandeered a Shi'ar vessel, but upon learning of D'ken's catatonic state, transferred his thirst for revenge upon the whole Shi'ar empire.
Recently Vulcan revived D'Ken from a coma. Not long after that event D'Ken reclaimed his title, ruler of the Shi'ar Imperium. He later performed the wedding ceremony of his sister Deathbird to Vulcan. Once the ceremony was completed, Lilandra and those Shi'ar loyal to her attacked the ceremony. D'Ken made quick work of the invaders and captured his little sister. While he pondered whether he should kill her or not, Vulcan took revenge for his mother's death, by killing D'Ken and gaining control of the Shi'ar.