Often taking the form of a woman, Death is the personification of death. She came into existence with Eternity, Infinity, and Oblivion at the start of all existence. Like her "siblings" she is nearly omnipotent.
Death rarely speaks, usually deploying servants to speak for her. She can release a soul from its body and send them to their final destination. She can also bring souls back, if not already in the possession of another (for instance, a god would have rightful ownership to a devout worshiper). In fact, the only souls out of the reach by death are those claimed by others, such as those who have contracted their souls to Mephisto.
There are also others who have a level of immunity to Death's "gift", such as immortals. Still others have been refused Death's gift personally, like the Elders of the Universe; one of their own, the Grandmaster swindled her in a contest.
Major Story Arcs
Death has also garnered her own followers, notably Thanos. She brought Thanos back to life because she sensed an imbalance in the universe and because of Eternity and Galactus trying to override her power and the actions of the In-Betweener. She believed that if the populations of the universe continue to climb that they will all end in disaster, giving her more souls than her power can handle. She tells Thanos to kill fifty percent of the universe's population. He eventually becomes infatuated with her.
Thanos gains the permission of Death to seek out the Infinity Gems to help him achieve his task. Through this she is able to get her revenge on the In-Betweener, when Thanos steals the soul gem from him and leaves him at the further mercy of his enraged masters. He obtains the final five gems and returns to Death. He claims his love for her and believes that they can rule at each others side now. She creates him a throne next to her, but she will still not speak with him. When he questions this, he is told that he is now her superior and they are not equals.
When Thanos gets the Infinity Gauntlet he planned to rule all the universe with Death by his side. Yet no matter what he did, she was not impressed. With a snap of his fingers he killed half the life in the universe. She still did not show any interest. Thanos finally becomes angry and sends a devastating shockwave across the universe. To spite her further, Thanos creates a companion for himself named Terraxia and tells Death he does not require her love any longer. This is just a plot for his love for her is undying.
Death eventually turns on Thanos and joins the cosmic beings in their attack on him. Thanos is deeply hurt by this. He still cannot obtain her love even with all the power in the universe.
The Silver Surfer
Death soon found what she didn't see in Thanos in the Silver Surfer. She had chosen him for his ability to bring death to untold billions. She plagued his mind with dreams of the deaths he had caused. She tried to make him her consort by force, but her minions were no match for the Surfer. Seeking information, the Surfer sought an unlikely ally - Thanos. Thanos agreed to help the Surfer but was outraged that the Surfer would be chosen as consort instead of himself. Through trust, he captured the Surfer and took him to Death's realm.
Thanos made his last appeal to be by Death's side and offered the Surfer to her. She accepted, but Thanos wished to be her love in exchange for his gift. Once again he has shown Death that he does not wish to serve her but to barter with her. She refuses Thanos once again. Angry, Thanos frees the Surfer and they work together to defeat Death's minions. Before they escape, Death lets it be known that Thanos is forever barred from entering her realm ever again and he shall live forever.
Lady Death was then met by a death god of another galaxy known as the Walker. He courted Death and she accepted him, much to the dismay of Thanos. As a gift to her, the Walker took the lives of all those in his galaxy into himself to offer to Lady Death. This gift disgusted her and she refused him, causing the Walker to become extremely angry. He decided that he would kill her for what she had done. This would cause utter chaos to the universe.
Thanos would easily forgive Death for her actions and protect her. He hid her while he could take out the Walker. Death hid herself in Marlo Jones while Thanos teamed up with Captain Marvel and Thor to defeat the Walker. In fact, the reason Marlo was even brought back to life was the fact that Death was inside of her, causing her to see ghosts of the dead who were drawn to her. After they successfully slowed the Walker down, Thanos and the others led him to Purgatory, where none could die including Death.
Walker saw through Marlo and realized the truth of where Death was hidden. Since Death cannot handle suffering, Walker used Marlo's love for Rick Jones in an attempt to get her to end her own life. But this backfired on Walker. Death would have given her life to end the suffering but being in a human host changed her traits to those more human, and far less forgiving. Death attacked Walker and removed the billions of souls from him, causing him immense pain and an eternity of agony.
Death returned Marlo to life, but as a result of Walker's torture, Rick Jones remained in an aged state and lost one of his arms.
When Thanos went on a pilgrimage to the Kyln, a prison on the edge of the universe known as the Crunch, Death appeared before him as a human girl. This is the moment she chose to finally speak to the Mad Titan, who at this point had given up on his desire to impress her. She claimed that she had desires beyond her essence and that she needed more than just death. She tells Thanos that she has always loved him as much as she is capable of such an emotion and asks for Thanos to find a way to love her the way she has always wanted.
Before Annihilation, Death came to bear witness to the coming of the Annihilation Wave, describing the coming of something "wonderful".
Death, who usually avoids the temporal affairs, shows an unusual interest in Deadpool, the merc with a mouth. He is one of the few - if not the only - sane mortals that can see and interact with her. During his torture after his failure in Department K, she would often distract him with fantasy worlds for the two, such as dancing together or having a picnic. She was the reason he wanted to die during that time, so he could be with her. However, when Deadpool activated his healing power through his need for vengeance, he could no longer see or hear her which upset the plans she had for him. While they had a flirtatious relationship, she made it clear that they would never so much as kiss until after he died.
Thanos, jealous of her attention and affections toward Deadpool, makes sure they can never be together. In his efforts to keep them apart, he gives Deadpool's worst enemy, T-Ray, the power to bring Deadpool back to life after he was killed by Weapon X. Thanos also gives T-Ray a cosmic item, the Gemini Star, which would split Deadpool's personalities apart from him, leaving him nothing but a boring shell, unappealing to Death. Even though the plan failed, Thanos cursed Deadpool with a worse fate than death; with life, preventing Deadpool from ever enjoying Death's embrace.
Thanos Imperative and Chaos War
After the invasion of Lord Mar-Vell and his deathless minions of the Cancerverse during the Thanos Imperative, Death appears when Thanos is to be sacrificed by Mar-Vell. Instead of taking Thanos, she destroys Mar-Vell, who had already cheated death once in his reality. She had allowed Thanos' return from the dead to set the trap. After killing Mar-Vell, Death destroyed the entire Cancerverse.
During the Chaos War, the evil entity known as Mikaboshi begins attacking all the underworlds of the universe and taking the dead into his army. In response to this, Death leaves the reality, causing all those that are dead to a deathless state of limbo.
In What If ...? #49 " What If the Silver Surfer possessed the Infinity Gauntlet? Before the surfer is corrupted by the gauntlet he changes Death into a beautiful being. She became an "alluring guide to a higher plane." "cherished not feared."
Silver Surfer (1998)
In the Silver Surfer animated series, Death is called 'Lady Chaos,' most likely to tone it down since the market for the show was children. Her appearance differs greatly from her comic book counterpart. She remains the target of Thanos' obsession.
Lady Chaos is voiced by Lally Cadeau, who also provided the voice of Moira MacTaggart in the X-Men animated series.
Deadpool (360, PS3)
Death is slated to appear in the upcoming game.