Cal'syee Neramani is the oldest of the four Neramani children to the ruling house of the Shi'ar Imperium. Despite this she was denied right to rule the Shi'ar due to a prophecy that declared that she would commit great evil. She was exiled after murdering her sister and mother in order to seize the throne. Cal'syee fled to Earth where she took the name Deathbird. Deathbird was an enemy of the original Ms. Marvel, and has fought her several times.
Some time after Lilandra inherited the title of Majestrix of the Shi'ar empire, Deathbird decided it was high time that she claimed her birthright and claim the throne for herself. Deathbird allied herself with Samedar and the alien parasites called the Brood, in a bid for the throne but her allies were defeated by the X-Men. She however managed to depose her sister and claim rule of the Empire. Cal'syee was deposed by War Skrulls impersonating Charles Xavier & the Starjammers who aided Lilandra and the X-Men in restoring Lilandra to the throne. However, with Lila Cheney's help Deathbird and the X-Men defeated the War Skrulls. In the aftermath Deathbird decided to leave the empire in Lilandara's hands, having grown bored of the endless bureaucracy.
During the Kree/Shi'ar War Cal'syee aided her sisters in a war against Kree. After the Shi'ar claimed the Kree Empires as the "spoils of war" Lilandra granted rulership of the Kree to Deathbird.
A while later, the Phalanx invaded the Shi'ar Empire and called upon the X-Men to help. Deathbird was amazed at Bishop's fearlessness and amazed that he stood up to her. They were physically attracted to each other and soon a romantic involvement began.
During their wanderings, the pair encountered the inert planetary mass of the Living Monolith on their way to Terra Firma. Curious, the two landed their craft and investigated the man-shaped planet. Suddenly Deathbird betrayed Bishop to a group of War Skrulls and was transported to Earth, to play his part in Apocalypse's plans. Deathbird was herself betrayed and transformed by Apocalypse into one of his Horsemen. With the title of War, Deathbird helped Apocalypse assemble the rest of the X-Men he would referred to as " the Twelve." However, Apocolaypse was defeated and Deathbird and the rest of the horsemen were scattered.
During the Maximum Security event where the Earth had been made a prison planet, with an energy barrier around the solar system, Deathbird possessed the key to unlocking the barrier. She and Bishop fought over the key with Deathbird finally daring Bishop to kill her. She opened the airlock and was sucked out into space before he could decide. Bishop closed the airlock, and then admitted to himself that he hated her.
When Vulcan was sprung from his cell by a member of the Shi'ar secret order, he was told to go down two levels in the prison. He did so, killing all in his path and when he destroyed the cell door, Deathbird emerged. It turns out that she was not killed when she was ejected into space--the Shi'ar Imperial Guard came and captured her before she died and locked her up in the highest security prison with the intention of keeping her there permanently.
Vulcan was captivated by Deathbird instantly, both by her beauty and by her ruthlessness. When Vulcan reconnects D'ken's neurological pathways and restored him to sanity, D'ken invokes an ancient Shi'ar custom that allows Deathbird and Vulcan to marry.
The couple are married in front of the M'Kraan Crystal, but decide to execute Xavier at the same time. The X-Men, the Starjammers and the Shi'ar loyal to Lilandara attack almost instantly. During the chaos that ensues Vulcan kills D'Ken (never having promised not to kill him) and assumes the throne of Emperor of the Shi'ar empire, with Deahtbird as his Empress. During the fight Polaris crushes the ribs of Deathbird's husband and she instructs the Imperial Guard, still loyal to the ruling family, to protect them as they flee.
During a prison break of the Starjammers by her sister and Rachel Grey, Cal'syee is severely injured. She is shown to be on life support but unresponsive.
As a member of the Shi'ar race, Deathbird has many of the traits and characteristics common to the her avian race, including enhanced strength, humanoid form, feathers, and hollow bones. However, she is what is known as a "genetic throwback", one whose genetics resemble those of one's ancestors, giving her more bestial birdlike features that most of her race has evolved past. Because of this, her body has more feathers than a normal Shi'ar including winged arms that give her the ability to fly under her own power and a larger crest of feathers on her face and head than normal. Her strength, durability, and agility are also enhanced past the other members of her race (normally Shi'ar can lift/press around a ton with Earth-like gravity, however Deathbird has stated she is on par with Gladiator). She also possesses dense, razor-sharp talons instead of nails which she uses offensively for hand to hand combat.
Along with her physical features she is a formidable combatant. Her skill is such that she trained Gladiator in unarmed combat. Deathbird has a violent and aggressive personality making her a dangerous opponent.
Here Deathbird appears as the leader of the Starjammers and as the emissary of the will of M´kraan Crystal, where she helps Gambit and his team to get to the M'Kraan Crystal. Her older brother D´ken managed to take over the entire control of the Empire, exiling her and killing their young sister Lilandra.In this reality she has a heroic role.
Star Trek : X-Men
Here Deathbird denies the wishes of her sister, and leads a band of Shiar troops into the Star Trek reality.
X-Men : The End
In this reality it is revealed that Deathbird sired a daughter along with Bishop, Aliyah. Eventually Aliyah kills her mother, due to being infected with a Brood Queen egg.
X-Men The Animated Series
Deathbird appeared in many episodes of the series, most notably the episode Beyond Good And Evil. Here Deathbird teams up with Apocalypse to attack and to overthrow her sister, Lilandra, in order for her to become the Empress of the Shi'ar.
Marvel Ultimate Alliance
Deathbird appears in Marvel Ultimate Alliance as an enemy in the Shi'ar Starcruiser level, sending her Imperial Guard after the heroes and Corsair. Here she has overthrown her sister Lilandra as Empress of the Shi'ar. She attempts to use the M'Kraan Crystal to become all-powerful after being defeated by the heroes.