Undeath
The undead are the fictional people who have died and still maintain some aspects of life. In many examples, the undead are immune to aging or even heal at an accelerated rate. Dracula is one of the most famous examples of the undead.
The Crimson King of Stephen King's The Dark Tower series has achieved a kind of immortality (as well as invincibility) by swallowing a sharpened spoon, thus dying yet remaining a conscious being.
The vampires of the Buffy the Vampire Slayer and Angel are immortal apart from the usual weaknesses of vampires- stakes, sunlight, decapitation and holy relics-, but it is clearly established that the vampire is merely a demon inhabiting the corpse of the person who was killed to become a vampire, possessing the memories of their human selves but incapable of genuine emotional connections such as love or guilt. The only exception to this rule is Angel- and later Spike-, as both vampires were eventually cursed with their souls, restoring their human selves while leaving them to deal with the guilt of what their bodies did while they were soulless.
The vampires of David Wellington's novel Thirteen Bullets and its sequels are virtually indestructible- they can only be killed if their hearts are destroyed-, but serious injuries sustained before they are turned will remain, such as one vampire lacking an eye and another missing the fingers of his left hand where they were bitten off, and the vampires continue to decay even after being awakened to their vampiric state; young vampires must hunt to feed their elders, with a vampire three centuries old being so decrepit that she would require six gallons of blood per night simply to walk on her own.
The roleplaying game Vampire: The Requiem, published by White Wolf Publishing, Inc., has undeath be the form of immortality held by vampires wherein their bodies are absent of all life functions such as breathing and heartbeat. They have theoretically infinite lifespans (and can even survive unprotected in the vacuum of space and under the crushing depths of the ocean), but they can be killed by sunlight, burning, or decapitation. Though they are also forced to watch as everything they knew in life withers away and they are unable to adapt to the changing eras of history. Because they are fallible predators, their humanity also begins to deteriorate, and a few become mindless/insane monsters called Draugr (also known as Revenants) as a result of losing all concept of being human. Such ravening monsters are always hunted down by other vampires, to prevent humans from learning of the existence of vampires.
The character Raziel from Legacy of Kain is a wraith who is capable of passing between the spirit world and manifesting in the living/material realm. Due to his secondary remaking into a wraith, he is beyond the cycle of death and rebirth so therefore cannot be killed. Any significant damage done onto him in the living realm forces him to seep into the spirit world to heal and any fatal damage in the spirit world simply transports him back to the Elder God or an activated checkpoint.
In the films Re-Animator, and subsequently Bride of Re-Animator and Beyond Re-Animator, Dr Herbert West creates a serum that has the ability to re-animate dead tissue and stop its decay. In Re-Animator, re-animated corpses are shown to show some emotion and intelligence if they're fresh enough. However, the antagonist in the story lobotomizes re-animated decaying corpses to make them his slaves.
Freddy Krueger of the Nightmare on Elm Street movies is considered to be immortal, as well. Though he was killed as a human, he exists as a "dream demon", who needs only to be feared to be able to enter people's dreams and cause them harm. Even without this fear, he can exist, either in "limbo" or in Hell. Because of this immortality, he can never be permanently killed. He can only be contained by being forgotten about, and thus prevented from ever entering dreams again.
In the movies and television series Highlander along with its franchise, the main characters of Connor MacLeod, Duncan MacLeod, and Methos, with other characters, are immortals since they are immune to disease and stopped aging after they had their first death, they can live forever and they only can really die when they are beheaded.
In the anime series One Piece, Brook consumed a cursed fruit before his death. One year after dying in battle Brook was reanimated by the curse, although only his bones and hair remained. Despite his apparent lack of internal organs Brook can speak, eat, drink, feel pain and carry out bodily functions such as burping and passing gas. These incongruous bodily functions and Brook's love of skeleton puns are a significant source of humor for the series. It is not yet known if Brook can recover from being killed a second time, though he states during the arc of his first appearance that he may have to be without his shadow until the end of his second life.
In the movie Pirates of the Caribbean: The Curse of the Black Pearl, Captain Barbossa and his crew have become undead after taking cursed gold coins out of an ancient chest cursed by Aztec gods. They look like humans during the day, but standing in the moonlight reveals their true nature: undead skeletons. While they still retain some of their human features like hair and in Captain Barbosa's case his nose, this form of immortality is a curse rather than a blessing since they can't die but also cannot feel life's pleasures or even pain. The film's sequel, Pirates of the Caribbean: Dead Man's Chest, introduces the crew of Davy Jones and the Flying Dutchman, who are essentially undead; Jones's duty is to collect the souls of those who die at sea, but over the centuries he has corrupted his purpose, cutting out his own heart after he is betrayed and abandoned by his lover and recruiting some of the souls he collects into his crew in exchange for their lives.
Read more about this topic: Immortality In Fiction