An admiral in the Shi'ar military, Lord Samedar allied with the exiled princess Cal'syee, better known as Deathbird, to join with her in a plot to destroy the Empress Lilandra, the Starjammers, and Earth.
As part of their conspiracy, a meeting of the Shi'ar Grand Council was raided by a terrorist commando force. Most of the ministers were slaughtered in the attack, and some were executed even after they'd surrendered, while Lilandra was kidnapped. The Starjammers were implicated and the trail left by the terrorists led straight to Earth. A fast battle force, led by Chancellor Araki and Lord Samédàr set out to rescue Lilanda and soon arrived in local Earth space. The fleet prepared to go to any lengths to liberate Lilandra or to avenge her, including reducing Earth to a cinder.
Araki provided Samédàr tapes on their past encounters with Earth and the X-Men, though Samédàr apparently ignored them.
Shi'ar forces pursued the Starjammer Corsair to Earth as he sought to inform the X-Men of the threat to their planet and to acquire their help. Narrowly escaping a Shi'ar dreadnought, Corsair crashed at Professor Xavier's estate and was rescued by Cyclops and Storm. The Shi'ar sent Sidrian hunters to capture or slay them, but the X-Men defeated the Sidri and Corsair slew them.
The Shi'ar next transported Corsair, Cyclops, and Storm, as well as Colossus, Nightcrawler, Professor X, Kitty Pryde, and Wolverine to their dreadnought. Araki revealed Lilandra's kidnapping, and he announced his intent to use Xavier's rapport with Lilandra to help locate her then to send a force of the Imperial Guard and combat troopers to rescue her. Fearing this course would lead to Lilandra's death and much collateral damage on Earth, Xavier invoked his right as Shivarn'n Halanau (Imperial consort) of Lilandra to forbid this. Samédàr considered humanity to the barbarians and their lives and planet to be beneath their concern, but Araki agreed to delay the invasion of Earth for 24 hours, allowing Xavier and his X-Men to try to free Lilandra without harm; however, Araki required two of Xavier's students as hostages as a show of good faith. After discussion with Cyclops and Storm, Xavier chose Kitty and Nightcrawler to stay aboard the dreadnought, and Xavier telepathically shared all of his knowledge of the Shi'ar with Kitty.
Back on Earth, the X-Men sought help from the Avengers and Fantastic Four, receiving only Tigra from the former. In trying to reach Lilandra telepathically, Xavier was struck by a psionic ambush, though he did learn she was in Manhattan. Meanwhile, Deathbird and the Brood ambushed Storm and Corsair as they walked the streets, but the X-Men and Tigra soon arrived to aid them. Ultimately, Deathbird captured Xavier and nearly slew Colossus, taking the former with her as she and her allies escaped in a starship.
The Starjammers picked up Corsair and the remaining X-Men and then took Colossus to emergency surgery. Samédàr taunted Kitty and Nightcrawler with an update, showing them the near-fatal attack on Colossus and then mockingly told them he had no further information on the teammates' fate. Samédàr then reported to Deathbird that Earth would be destroyed on schedule, promising that he would deal with anyone who tried to interfere. He further congratulated Deathbird on her victory over the X-Men but warned her that they had joined the Starjammers and would be pursuing her. Deathbird criticized Samédàr for not stopping the X-Men, but said she would take care of him and reminded him that the destruction of Earth was his responsibility.
Meanwhile, the Starjammers caught up to Deathbird's ship, only to be grabbed by the giant Acanti-ship used by the Brood. Despite this, the X-Men and Starjammers fought their way past the Brood, rescued Lilandra, and escaped. However, the Starjammer had been damaged, requiring repairs that would not allow time to notify Araki that the Majestrix was safe. Meanwhile, Samédàr murdered Araki and took command of the operation.
The X-Men managed to expedite repairs on the Starjammer, but when Xavier tried to reach across space and telepathically contact Kitty or Nightcrawler, he was struck down and rendered comatose by an alien presence within him (a Brood embryo). The crux of his message got through to its targets, however, but not only could they not reach Araki but they then heard the Shi'ar fleet being called to battle stations. Shi'ar guards were sent to slay the captive X-Men, but they defeated their attackers and escaped their cells, only to find Araki had been murdered. Correctly suspecting Samédàr, they plotted to gain aid from the Imperial Guard, who were loyal to Lilandra.
Samédàr ordered the Shi'ar to target Earth's major population centers with their missiles, dismissing questions of Araki's plans and absence and ordering the captain to obey his commands. Using a Shi'ar costume device and the implosions of Nightcrawler's teleportation, Kitty impersonated Phoenix and delivered a warning that Earth was under her protection and that they should attack Earth at their peril. Nightcrawler then teleported the Imperial Guardsman Oracle away and let her read their minds to learn of Xavier's message. Oracle then summoned Gladiator, Starbolt, and N'rill'irēē to her side and shared the information with them. However, Warstar and a group of Guardsmen and Borderers loyal to Samédàr and Deathbird then broke in and announced that a new order was about to embrace the Shi'ar, and that those who had no place in it would be eliminated. The two sides battled, but then Samédàr used a Brood weapon to incapacitate everyone in the room.
Wishing his defeated foes, including the Shi'ar Captain K'rk who had opposed him, to witness his final victory, Samédàr then ordered his ships' weaponeers to fire, and a bolt of anti-matter plasma erupted forth, aimed at San Francisco and intended to devastate North America. However, the Starjammer then flew in, flying far faster than the speed of light as it skidded out of warp space, and intercepted the beam, defusing it with its shields.
Lilandra transmitted a message to the Shi'ar revealing that she was unharmed and insisting that no harm be done to Earth. Gladiator informed her that the attack had been initiated by Samédàr, who was in league with Deathbird and had murdered Araki. Lilandra ordered the arrest of Samédàr and the release of the loyal Imperial Guard. She put K'rk in command of the Shi'ar fleet and instructed him to withdraw beyond Earth's moon pending her imminent arrival.
Samédàr's current whereabouts and activities are unknown. However, the Borderers and Guardsmen who aided Deathbird were among the alien convicts sent to Earth when it was briefly deemed a prison planet by the Intergalactic Council, but Samédàr was not among them. It can thus be speculated that he was executed for treason.