Life Energy

Spiritual fuel that runs the body and mind, generally invisible to science (but not Lost Technology). Life Energy may be the same thing as the spirit, or rather just some sort of spiritual Life Meter. Even the hardest of television Science Fiction can't seem to help but use this trope at one point or another, even though modern science doesn't give it a leg to stand on...nor can it demonstrate the untruth of the claim, since the basic nature of biological life remains imperfectly understood. Vitalistic claims are a-scientific, but not counter-scientific.

Relatedly, even the hardest-nosed Nietzscheans and Randians have been known to go on (the latter at length, of course) about the "life-force".

In Anime, is often the vampire alternative to drinking blood, but also is often used to explain why human blood is better for vampires than non-human or why they can't feed on the dead. It just sates their Horror Hunger better. Many Anime antagonists, especially enemies of Magical Girls, are thaumovores: they feed on Life Energy or use it to power their evil plans. A clear sign that a character is a life-force sink is the spontaneous death of flowers around him or (usually) her.

The victim of Life Energy theft may recover if only a little of it is taken, or else may end up in a coma that is unexplainable to mundane doctors. Other results include becoming a walking Empty Shell, or outright dying as the body becomes a skeleton or even crumbles to ash.

In the west, stealing Life Energy tends to be less common than giving Life Energy. Infusing someone with Life Energy (or sometimes Generic Energy) can be used to revive those who are critically injured, or to grant temporary superpowers. Watch out for Phlebotinum Overload, however.

It's connected to souls, Hermetic Magic, Ki Attacks, Psychic Powers and other superpowers; see also Mana. In Role Playing Game terms, it's the combination of Hit Points, Magic Points, and Experience. Transferring it may cause physical changes that are Liquid Assets. Occasionally, part of an Equivalent Exchange to power an Artifact of Doom or Evil Weapon.

It should be noted that somehow many spacecrafts' Everything Detectors can scan for it, and yet somehow only pick up humans or things like humans. Bugs, rats and the vast trees of Canada-in-the-Pegasus-Galaxy do not make the grade, so obviously life signs automatically imply sentience (or at least really-bigness).

Anyone whose life energy is especially Supernaturally Delicious and Nutritious is in for a hard time.

Not to be confused with the NES space jet game of the same title, or the 1985 sci-fi movie.

See also Aura Vision and Anatomy of the Soul. If Life Energy is used to power a device, the thing powering it is a Living Battery.

Anime & Manga

 * Tien from Dragon Ball and Dragon Ball Z's signature technique uses his life energy, making it one of the most powerful techniques in the series.
 * Goku's ultimate technique, the Spirit Bomb, draws in small amounts of life energy from everything around it and unleashes it in a huge explosion.
 * Goes by the name Power of Existence in Shakugan no Shana. Losing any amount of it turns a human into a Torch at best, doomed to eventually have never existed.
 * First-season Sailor Moon villains, The Dark Kingdom stole life energy from humans in to free the Big Bad from her prison, as did the mini-arc villains in the second season, Ail and En who feed it to the magic tree that kept them alive.
 * Key the Metal Idol has a Corrupt Corporate Executive engage in Life Energy harvesting far more effectively than the Dark Kingdom ever did. For example, random people at rock concerts, where it's expected for there to be fainters.
 * Magical Girl Lyrical Nanoha's second season had the antagonists stealing magical power from mages (magical beasts when they could, though) in order to complete "the Book of Darkness." Fortunately, people can recover from that, and depending how young they are, their powers can also completely replenish.
 * Fullmetal Alchemist, the anime.
 * A different twist occurs in the manga. While alchemy largely draws on natural energy, such as plate tectonics, the greatest source of energy is.
 * Bokurano. The giant robot is powered by the Life Energy of the pilot.
 * The manga even hints that the younger the person, the more life energy he/she has, and the more powerful Zearth becomes.
 * The premise of Yu Yu Hakusho implies that life energy is essentially the same as spirit energy but is the necessary portion reserved to keep the body running. It seems to be a fair amount, to the point that a person drained of spirit energy can still throw a large enough energy attack to win a battle, provided that they're okay with being dead afterwards. All but one of the four major characters are guilty of this at one point or another, and the main character employs it as a reliable backup strategy.
 * Seeing that he's half-demon and can pretty much reincarnate at will, this tactic is pretty cheap.
 * Michel of Mermaid Melody Pichi Pichi Pitch steals it from powerful beings. This usually means absorbing them into himself (as he tried to do with Seira), but he left Kaito alive to blackmail Lucia with. Near the end,
 * Chakra in Naruto is a combination of a person's physical and spiritual energy. While it can be used to power jutsus and enhance the body, it is also required to keep the body functioning. If you use up enough that your body has less than the minimum needed for the body, you suffer from chakra exhaustion. If you use up absolutely all of it you die.
 * Natural energy found in the world acts as a third component of chakra if a person is able to learn how to use it. It's present wherever there's life and greatly enhances the body, but drawing too much will overwhelm the user's own chakra and transform them into stone.
 * In a twist, it was revealed that.
 * Chiyo can also use life energy to heal, albeit with Equivalent Exchange involved. The first time, she transfers her life energy to heal a mortally wounded Sakura, saving Sakura but bringing herself to the brink of death. The second time,.
 * Bleach features vampire-like creatures called Bount, which drain the lifeforce out of their victims as opposed to blood.
 * Pokémon features Aura (described by Mei Ling as "life force") which is normaly used by Lucario's and, to a lesser extent, Riolu's (oh, and there's the occasional human with Aura abilities). Needless to say, an awful lot of cool powers come with it. How about unlimited vision when you've got your eyes closed, so you'll technically never go blind? Or a cool ball of energy that you can summon out of nowhere?
 * Life Energy is a major theme in many Gundam works. Various Gundams in later UC stories have Gundams powered by various bits of Magitek in all but name that run on their pilot's life energy. Used much more blatantly in the less serious G Gundam. Gundam Wing uses it less, but it does feature killer robots who can sense the life energy of their targets, even through metal, Infrared X Ray Camera-style.
 * The plot of Prétear pretty much revolves around Life Energy (Leafe). In the manga version, this gets downright cruel: the Knights can only use their Elemental Powers at the expense of their own Leafe; as a result, whenever Himeno is performing attacks as the Pretear, she drains the Life Energy from whichever Knight she is currently merged with. The Pretear can also create Leafe, though. Needless to say, the monsters and the Big Bad of the series really like stealing Leafe...
 * In Saint Seiya, the key to the Saints' power is their cosmos. Whoever can burn his cosmo to the higher level wins, no matter how injured or weakened they are.
 * In Katekyo Hitman Reborn there's Dying Will, which started out as just something that tapped into your hidden potential to keep you from dying without fulfilling some desire. Later on though, it became the basis for all forms of attack and even has seven differently colored types with various powers and appearances, and is accessed through your personal resolution. They have a sky theme (Sky, Sun, Storm, etc).
 * Now there are seven more flames with an Earth theme (Earth, Forest, Swamp, etc).
 * In Inuyasha, there are two kinds of souls: one is your true self, and one is the power that animates the body. Seeing how nobody reacts to Kikyo as a soul-stealing Complete Monster, she is presumably surviving on this second kind.
 * Busou Renkin has the Black Kakugane, which drains all nearby life energy.

Comics

 * This may be what the planet-eating Galactus in Marvel Comics feeds on.
 * The Life Entity of the Green Lantern Corps mythos is the embodiment of life, and thus, is made of pure Life Energy.

Fan Works

 * Paul in With Strings Attached has so much of this that when two wraiths feed on his life energy, they explode from overeating.

Films -- Live Action

 * Lifeforce, the naked space vampire movie, is all about Life Energy vampirism. And boobies.

Literature

 * Mercedes Lackey's Heralds of Valdemar series uses a fairly well-developed magic system that is based almost entirely around this concept. All living beings generate Life Energy, which drains away from them into the ambient environment, eventually collecting into Ley Lines. Where two or more Ley Lines meet, you have a Node, which is a massively powerful energy source that only Adepts can hope to use without burning themselves out. The ultimate destination of this energy is the nether plane, from which it then reenters the world through living beings. Mages are people who have the innate capability to store additional magical energy within themselves, see this energy, and instinctively manipulate it. It's also possible to manipulate it without mage talent via rituals or Blood Magic. A person wholly drained of life energy, whether from Blood Magic or spellcasting beyond their capacity, will lapse into a coma and die. Accordingly, it can also be used to heal people, although this is most efficiently performed by those with the specific talent for it.
 * Lackey's Children of the Night has 'psi-vamps' who drain energy from others. In this case the energy is tied to emotions -- they drain excitement at first, and later hate and fear. Also, a completely drained victim is usually not physically dead, but is emotionally/mentally burned out (described as a mindless hulk, with no chance of recovery).
 * The Night Watch series of novels has the "Others", a group of superpowered and supernatural humans forced to choose between good and evil when they first gain knowledge of their gift, can get energy from taking the emotions of normal humans and store it for later use. Some are actual vampires, and do need blood in addition to any life energy they get, albeit not necessarily human blood.
 * In the Harry Potter universe, Dementors require (and enjoy) feeding off people's happiness, making them quite depressing to be around. (Aptly, considering they are based off of J.K. Rowling's period of clinical depression following the death of her mother.) Anyone in their immediate vicinity is prone to becoming nearly-catatonic with sadness, desperation, etc. In more extreme cases, they can give someone a "kiss" by sucking out their soul and leaving behind an Empty Shell.
 * Also Tom Riddle absorbed Ginny's soul in Chamber of Secrets, causing him to regain physical form while she was reduced to a coma-like state.
 * In Lois McMaster Bujold's Paladin of Souls, this is happening to Illvin
 * In Bujold's The Sharing Knife books, Lakewalkers' magic is all about the manipulation of Life Energy.
 * In the Dark Visions series by L. J. Smith,
 * In H.P. Lovecraft's short story "The Colour Out of Space", the title monster feeds on the life energy of creatures that live near to where it lairs.
 * In The Dresden Files, human beings (and other living things) have a magical essence that is necessary to sustain life, but can be fed on by White Court Vampires and some other things, and which a Wizard (or presumably even a mundane, even he somehow had the necessary skills) can tap into to power a 'Death Curse', a spell of exceptional power that can be used to spectacular things...at the cost of one's life because the energy is all used up.
 * Also, in a later book, there is Soulfire. Makes your magic extremely powerful, by literally burning up your soul.
 * And, in Ghost Story, we find that ghosts can only attack or defend by using their memories---and all a ghost is, is memories, so...

Live Action TV

 * In the Korean Drama My Girlfriend Is a Nine Tailed Fox the titular multi-tailed fox (who has taken form as a beautiful human woman) gives a mortally injured man an "energy bead" to keep him alive.
 * Babylon 5 has Captain Sheridan die but then get resurrected with an infusion of life energy. He was told, however, that regardless of medical procedures, his body would just "stop" after a period of time. Another plot involved an alien artifact that transferred life energy (it was used for capital punishment ).
 * In Doctor Who, the Fendahl consumed the full spectrum of Life Energy, causing rapid decay of the corpses it left.
 * Also, "Forest of the Dead" subverts the usual rule about the Everything Sensor in regards to life forms: once the Doctor specifies that he's not interested only in humanoid life signs, the Library sensors report on every one of the billions of Vashda Narada spores.
 * When the Master comes back wrong in "The End Of Time", the Doctor tries to warn him that his awesome new powers are consuming his Life Energy.
 * Emotions get drained in Red Dwarf, too. A polymorph snacks on the most powerful emotion from four distinct characters. Never explored what would happen if multiple emotions got drained from the same character, but when you strip away the hero's sense of fear, you get suggestions like: "Why don't we take a nuke and strap it to my head -- I'll head-butt the monster into oblivion!"
 * The Wraith in Stargate Atlantis are essentially Life Energy Vampires. There are, however, some Techno Babble attempts to explain it as hard science, essentially implying the exact process is badly understood, and that speaking of "Life Force" is a handy though incorrect shortcut. The overall effect of Wraith "feeding", which is done through a special organ in their palm, is similar to Rapid Aging. They can also give back some of the stolen Life Energy, rejuvenating the subject or even bringing him back to life.
 * The Lifeforce Megazord from Power Rangers Lightspeed Rescue, which uses the rangers' energy.
 * Kamen Rider Kiva features Fangires, a stained glass-based vampire race that materializes crystal fangs in midair, sticks them into their human targets' neck, and drains the life energy out of their bodies for food, leaving the victim as a glass corpse that can be shattered with a single touch. (The words Life Energy are always in English for some reason.)
 * In Tin Man Azkedellia kills at least two people with this ability and  While she got better,
 * The Dark Kingdom in Pretty Guardian Sailor Moon stole energy from people in various ways, just as their animated counterparts did.
 * Tracker used this heavily. Each fugitive was in the form of a life force that took over a human body and killed the original occupant. Cole sucked out the life force into his collector when he caught up with them. Apparently, they were drained of life force when they were put in prison, and the life force was slowly returned as the sentence was served.

Tabletop Games

 * Dungeons & Dragons has many creatures that can drain life energy levels, such as many undead, succubus demons and so on. Class Levels being certainly the most hardly-earned feature of a PC, such creatures are greatly feared -- especially in 1st and 2nd edition, where such drains were permanent with no saving throw. Later editions have somewhat nerfed this power, to the regret of any serious GM.
 * Spelljammer also included lifejammers -- a spelljamming helm was a chair which allowed one to pilot a vessel into space by draining spell energy; a lifejamming helm ... well, you can figure it out from there. Lifejammers were particularly popular among evil beings such as neogi and undead, who were fond of subjecting their slaves and captives to this.
 * GURPS Aliens. The Gloworms feed on Life Energy by touching other living creatures. They can feed on animals but prefer sentient victims.
 * Call of Cthulhu (tabletop game). The Colour Out of Space monster feeds on Life Energy, just like the original version in the H.P. Lovecraft story.

Video Games

 * Mana from Tales of Symphonia. When the world decays, a Chosen sets out to restore Mana,
 * Prevalent in Nasu Kinoko's works (the Nasuverse).
 * Tsukihime: ability ("Plunder") is taking the life energy (and heat, apparently -- there may not be much of a difference) of others through Prehensile Hair that moves at the speed of thought, hits like a sucker punch or a spear, holds like a python, and is invisible even to her own eyes. Fortunately, the drain itself doesn't start or finish instantly.
 * Fate/stay night: the Mages (Masters) and their Servants have the ability to manipulate the life energy of others (mana) both willingly and unwillingly.
 * The title creatures from Metroid drain the life energy from any animal unfortunate enough to encounter it. The Space Pirates tried to use science to explain the phenomena, but could find absolutely no trace of this "life energy", only the proof that it undeniably was occuring.
 * However, Samus's suit is able to see and absorb the life energy of defeated enemies for use as shielding or ammunition, likely due to both the suit and Metroids being created by the Chozo.
 * The Legend of Zelda series commonly refers to Link's HP as "life energy." Whether or not this is a link to a spiritual force really hasn't been said, except if you maybe count Phantom Hourglass.
 * In Minish Cap, the Light Force was directly tied to Princess Zelda's Life Energy. Draining away the Life Force from her body can kill her, which leads to a timed section near the end of the game.
 * The Chromotap device in Syndicate Wars draws Life Energy from the recently dead to heal your agents (who probably killed them.)
 * One character in the Chzo Mythos is able to draw out the life energy of others by using a sacrificial knife.
 * Raziel from the Legacy of Kain series typically feeds on the souls of the slain, but he can also snack on friendly humans. If he only drains a little, they'll get tired but eventually recover. Too much and they'll die, and then the other humans stop being so friendly.
 * Life Energy was first offhandedly mentioned in the Fire Emblem series in Genealogy of the Holy War under the name Aegir, but had a much bigger role as the Big Bad's main power source in the seventh game, where its name was localized as "Quintessence".
 * Mantra from Asura's Wrath is this, and is also created via Human prayer. Along with powering up Technology and the Demi-gods Genetically modified to use them, It also can be used in weaponry. Also played around with, in that

Web Original

 * Tied into ley lines (as used by mutants like Fey) and also Ki (as used by mutants like Chaka) in the Whateley Universe.
 * In Elcenia, this is the fuel used for kamai. Kyma can refuel with food and sleep, pretty similarly to if they had physically overexerted themselves, and they can also sense life energy.

Web Comics

 * Tristram's power in Earthsong is the draining and replacement (thereby, healing) of Life Energy.
 * In Thunderstruck, it is explained that vampires don't feed on blood per se, but on the Life Energy it carries.
 * Medicine in Girl Genius seems to rely on "Galvanic energy," which is usually fed through big machines, or from the waters of the Dyne.

Western Animation

 * In Adventures of the Galaxy Rangers, the Queen uses Life Energy to create psychocrystals, which power Slaverlords, wraith-like beings she can see, hear, and speak through. Humans Are Special in a BAD way in this universe, as they are the best species she's found to power the things. Fortunately, she only was able to make two human crystals in the entire course of the series, and only able to hold onto one. Unfortunately, that one crystal happens to be made from Zach's wife.
 * In Wakfu, the Life Energy is called... wakfu. It is the power source of all magic, and present in every living being, plants like animals. Nox, the Big Bad of the first season, aims at draining as much wakfu as possible, to next feed it to the Eliacube, an Amplifier Artifact that can boost his powers beyond those of any time-magic user before, or even beyond those of his god, Xelor.
 * The Parasite in Superman: The Animated Series is basically a male villainous Expy of Rogue. Humans usually wind up unconscious and twitching a little. He can also gain access to their memories, and sound like them. When he does it to Superman, however...
 * The Parasite is hardly an expy of Rogue, as he is far the older character; he was around in the 60s.
 * Star Trek: The Animated Series episode "The Lorelei Signal". The females of the second planet in the Taurean system can only survive by draining the life energy of male humanoids, which causes the males to age and die.

Real Life

 * Starting with Franz Mesmer's "magnetic fluid", every few decades someone will propose essentially the same theory, which all fall under the label of "vitalism". After Mesmer there was Carl von Reichenbach's "odic force", then Wilhelm Reich's "orgone energy" and most recently zero-point energy and other quantum mechanical phenomena have been adopted.