This is a type of monster that is immune to starvation and dehydration, it may not even have to sleep or breathe. Much like the Energizer Bunny, it just keeps going and going and going. Perpetual Motion Monsters are either explicitly supernatural (e.g. The Undead), a set of super advanced Mecha-Mooks, or both.
Science savvy characters may discuss how implausible it is that the walking dead in a Zombie Apocalypse, despite craving brains, can keep walking 24/7 for years or longer without any kind of sustenance. Compounded by that fact that though decayed they never actually rot enough to stop posing a threat. Frequently, The Professor / Mad Scientist will fear (or marvel) at the potential these thermodynamic law-breaking monsters represent. This is the whole idea behind undead armies in any setting— they are weak but fearless and while slow, they can march 24/7 with no supply lines, all while assimilating the enemies' fallen.
This is usually a Justified Trope for Ghosts, Dem Bones, and Elemental Embodiments since they aren't really biologically based, so they don't need traditional food sources. Although, they may need some other form of energy or material as a Power Source (like prayers or lighter fluid), thus averting this trope. For Mecha-Mooks and other technology based creatures they usually incorporate some near infinite Power Source (or a means to tap into an external one) and some kind of Healing Factor.
A character with the right type of Immortality who eats and drinks can still be a Perpetual Motion Monster. Their form of immortality specifically prevents them from dying due to starvation and dehydration, though they probably won't enjoy the experience... unless it's a case of them not actually needing to eat or drink, and thus they don't feel hunger or thirst in the first place. Such a character can make for a truly Implacable Man — nothing can keep them from their goal, not even the ravages of time!
For extra threat, the Perpetual Motion Monster is also usually unaffected by dismemberment (except for the "annoyance" of a lost limb, though a needle and thread can solve that). For extra extra threat, it's also a Super-Persistent Predator; since being a Perpetual Motion Monster means it doesn't actually need to eat except for the pleasure of it, it can afford to go to the ends of the Earth in pursuit of that one tasty hero-sized morsel.
See also You Can't Kill What's Already Dead, where the undead just shrug off any injury for similar reasons as this trope.
Related to The Sleepless.
- The synthetic humans in Biomega come pretty darn close. They can live for months without food and for weeks without water and not lose efficiency.
- Androids 16, 17, and 18 in Dragon Ball Z are "infinite energy models" according to their creator, Dr. Gero (compared to Androids 19 and 20 who must absorb energy from people instead). 17 and 18 thus specialize in Victory by Endurance fights, because unless they get overwhelmed or badly injured, they'll always win by virtue of never getting fatigued.
- Super-17 from Dragon Ball GT had the best of both worlds: He had the "infinite energy" power source, but could also drain power through his hands to increase his power level (and conveniently enough, weaken his enemies at the same time). Unsurprisingly it takes a combination of Fighting from the Inside from 17 and 18 pressuring him to even bring him down to the same level as the Z fighters.
- Majin Buu is also this. One of the most dangerous things about him is that he never loses strength, and his Healing Factor is so powerful that giving him a few free seconds will result in Buu healing completely, just as ready to fight as before. You need to consistently pressure him with powerful attacks until he is reduced to subatomic particles, or it will ultimately not matter.
- Alucard, a vampire, in Hellsing was sealed in the Hellsing estate for decades without blood and was still "alive". Granted, greatly weakened, and dessicated into a husk, but he still woke up when exposed to blood.
- Chiropterans in Blood+ won't die from starvation, as happened to one imprisoned in a concrete block in Russia. It was emaciated but still awake and capable of killing.
- The eponymous warriors in Claymore do not need to eat or drink except in small doses. Though, when they awaken, they eat human flesh regularly, but can go without for a long time (several years), but it does weaken them...
- The Angels in Neon Genesis Evangelion are explicitly stated to have an infinite power source in their bodies: the S2 Organ. Therefore, while alive, they have no need for sustenance, rest, etc. and are effectively immortal, though they can still be killed if damaged enough.
- The Titans from Attack on Titan. While lack of sunlight and fatigue can slow them down, they do not age, sleep, or thirst and do not need the human flesh they eat.note They even regenerate biomass instantly and out of nowhere while thriving.
- JoJo's Bizarre Adventure:
- Battle Tendency has Kars himself. Once he evolves into Ultimate Kars, there is simply no way for him to die. The only way Joseph could get rid of him was to shoot him out of orbit.
- Vento Aureo has the Stand "Notorious B.I.G.". It decomposes anything it touches, moves incredibly fast, and since it emerges when its user is dead, literally cannot die. Its weakness is that it can't see, so it has to use motion detection to go towards the fastest-moving object within range. Bruno's gang "defeats" it by dropping it in the ocean, so it uselessly attacks waves for the rest of eternity.
- Most dragons in Miss Kobayashi's Dragon Maid require external sources of mana (like with Kanna plugging her tail into a power socket), but Tohru and Lucoa are both capable of generating their own. Other dragons are capable of using the mana that Tohru radiates, but Ilulu states that it tastes awful.
- Superman foe Doomsday.
- The Incredible Hulk cannot be stopped except by being calmed down by a close friend or loved one. Trying to subdue him by physical means only makes him angrier and his strength is proportional to his anger and has no upper limit.
- Reed Richards in Marvel Zombies cites this trope as his justification for believing the zombie plague is the next step in evolution. He then proceeds to infect the rest of the Fantastic Four. In this case, Reed Richards is Genocidal.
- Scrooge McDuck once had an immortal zombie (called Bombie) go after him for very long time, often walking nonstop across oceans, being frozen in ice for long time, and so on.
- The zombies in The Walking Dead are Perpetual Motion Monsters, like most zombies. They technically don't last forever, as the characters have started to notice that more and more Walkers are extremely rotted, and on the verge of falling apart.
- For X-Men foe Juggernaut, this is basically his power (mystical power in the comics, mutant power in the movie).
- Taken to an interesting new height in Fear Itself. While possessed, he truly becomes unstoppable. At some point in the event, he calmly walks to San Francisco from a dozen miles away, while the X-Men try a bajillion plans to stop him. Teleporting him away does nothing, he just reappears instantly. Digging a giant trench in front of him does nothing, somehow he strolls calmly across thin air! The X-Men ultimately have to resort to contacting the god that empowers Juggernaut and informing him that a second god has possessed his avatar. Cytorrak takes his power away from Juggernaut and transfers it to Colossus.
- Willy Pete from Empowered is an incredibly powerful fire elemental that eats superhuman flesh because he likes the taste, and because super-strong flesh is the only food that his mouth won't instantly incinerate. Being a fire elemental, he doesn't actually need to eat.
- Judge Dredd: The Dark Judges are undead foes of Judge Dredd. They don't need food or water and will chase down their victims either until that victim is dead or their own bodies have been destroyed. It's unlikely that their bodies even can decay on their own, as they are really being fueled by their spirits' psychic power. When Judge Dredd has a piece of skin from Judge Death's original body analyzed by the techs, he's told that it's several hundred years old.
- Paperinik New Adventures manages to provide an heroic example in Xadhoom: having effectively turned herself in a star in a humanoid body, her immense powers never run out, and to make things worse she can come back from complete disintegration. She qualifies for the 'monster' part by being a Humanoid Abomination (something she's all too conscious of), and for being out to commit genocide on the Evronians for destroying her homeworld and her race.
- Drax the Destroyer was originally created specifically to kill Thanos. His artificial body doesn't need to eat, drink, sleep, or breathe, doesn't age, is incredibly difficult to seriously injure, and if destroyed, regenerates from his own remains (or from the soil where he was originally created, if there isn't enough of his former body left). Unfortunately, in the decades since Drax's original creation, Thanos has had several power-ups, reducing Drax from his original "grim avenger" status to a perpetual annoyance (for Thanos, not his minions). These days, he doesn't even rank among the Mad Titan's top ten enemies (though he did manage to score the coup de grâce during Annihilation).
- Wonder Woman Vol 1: Circe raises Artemis, Diana's long dead predecessor in the role of the Amazon Champion, as a skeletal figure who needs no sustenance and cannot seem to be harmed nor reasoned with as she attacks the Amazons seeking "revenge" for her abandonment and lonely death in the outside world.
- Enjin works this way in The Bridge. Being composed of solid dark magic, it need not rest, eat, or drink to continue pursuit of its quarry. Its only weakness is that if separated from its master Bagan for long periods of time, its body will start to deteriorate.
- Jovian and Jacqueline Kikion of Rosario Vampire: Brightest Darkness are this, thanks to being enhanced with Alucard's blood. They have no known limit to their power levels, and can fight non-stop without ever tiring.
- The eponymous army in Hellboy II: The Golden Army is a positively inhuman combination of perpetual motion monster, The Juggernaut, and regenerating. It was an ancient weapon Gone Horribly Right to the point the elf king who commissioned it sued for peace after it massacred a human army.
- The monster from the movie version of Peter Benchleys Creature survived locked in a cage on the sea floor without any food or room to move for decades without any debilitating effects. The book version averts this by having it stalk out of its cage in a deep sea trench ever so occasionally.
- The original Terminator movie made the eponymous cyborg sound like this trope, until the second film subverted it by revealing that his power cell would eventually run out....after 120 years.
- In the Underworld (2003) film series, the first Lycan William Corvinus was sealed in a tomb for 600 years. Once he's out of his coffin, he's at full strength. He clearly wasn't in suspended animation.
- Referenced in Pirates of the Caribbean: The Curse of the Black Pearl, when undead Barbossa banters with an equally-undead Jack that they could keep fighting their duel for eternity.
- The monster from It Follows may not move fast, but it will never stop chasing whoever has the curse until they're dead. Then it goes after the last person who had the curse. It doesn't help that it is able to take on the appearance of anyone.
- In Robert E. Howard's Conan the Barbarian story Black Colossus there's a giant venomous python which slithers out of a 3000 years old tomb and is still lively and in top shape.
- Similarly, the basilisk in Harry Potter and the Chamber of Secrets had apparently been stuck there since the founding of the school, waiting for its master's heir to come and release it.
- In The Lord of the Rings:
- The Watcher in the Water is a massive squid-like beast living in a lake just outside Moria. It had been driven from the deeps of Moria into the flooded valley as a guardian and to trap the dwarves inside Moria. A creature that big just hanging around in caves needs to have SOME of this going on though.
- The Balrog in Moria isn't slowed down at all by being entombed underground for millennia, thanks to being an immortal angelic spirit before its corruption by Morgoth.
- The cauldron-born from The Chronicles of Prydain are deathless zombies animated by the Black Cauldron. They do not eat, sleep, breathe, or get tired, and they feel no pain.
- In The Zombie Survival Guide zombies are explained by the virus which creates them replacing their mitochondria and taking over respiratory functions so they no longer need to eat or breathe (...somehow) and slightly more plausibly, delaying decomposition by protecting the body from rotting as the immune system would have. The later part of the trope is also averted, since zombies do rot away after a few years, unless they're in arid environments or end up being frozen.
- Not "monsters" per se, but Discworld Golems just keep going and going and going and going. They're used for menial, tedious labor typically, since they don't have to sleep and, for the most part, enjoy it as much as they can enjoy anything. They even use this as a form of passive-aggressive protest via Literal Genie; they're smart enough to take initiative and can read the intent behind orders, but if you mistreat them, they're liable to fight back by doing exactly what you say, constantly, until someone figures it out and tells them to stop. This can mean that the golem you asked to "pump some water" doesn't stop until your shop's street is partly underwater.
You can hide, but you can't run!
- A more traditional version, also a golem, is Mr. Pump in Going Postal. As Moist's parole officer, it's explained that even though he can only walk while Moist can run, get a horse, a cart, or even a boat, he will never tire, and never stop until he catches up to him. After one demonstration of this, Moist gives up on trying to run away.
- In Brandon Sanderson's Warbreaker, there are two. The first and most well-known are the Lifeless, an army of Implacable Man zombies who do not need to rest or eat or drink or breathe. They obey any command given to them by anyone with the proper code-words. Whoever controls the army of Lifeless has control, more or less, over the kingdom.
- Much worse, as it turned out, were the Phantoms of Kalad — like the Lifeless, but made of stone and thus damn near impossible to kill.
- In The Synthetic Men of Mars, a malfunction at an already imperfectly working cloning facility produces a constantly growing mutant entity that consists of a huge blob of human flesh and random body parts. It's stated that if it hadn't been fire-bombed from above until there was nothing left, it could have grown forever by eating itself. Just think of the potential applications of something like that on a starving planet.
- The zombies in Diario de un Zombi, minus some very gradual wear and tear.
- In Mortal Engines, the cyborg zombie Stalkers are explicitly stated to draw energy from the environment somehow, and are otherwise capable of functioning without needing to eat or recharge or refuel for an indefinite amount of time. And the oldest Stalkers, the ones made with Lost Technology, can't even die. They just go dormant, ready to fight again as soon as they're repaired and reactivated.
- Lampshaded at one point; when a stalker expert is asked by Fever Crumb(who is rather confused about how Stalkers are possible) how they work, she responds with "molecular clockwork". Fever instantly identifies it as an In-Universe Hand Wave.
- "That is not dead which can eternal lie..." Lots of examples in the works of H. P. Lovecraft.
- In Firebird (Lackey), the dragon and the "dolls" in the Katschei's palace are implied to be mechanical in nature, possibly even robots that obey short logical orders. More than that, neither need sleep or fuel, though the dolls do seem to "tire" and need a day to recharge.
- In the Left Behind series, one of the perks Nicolae Carpathia gets from being possessed by Satan is that he no longer needs to sleep, drink or eat; the evil power of Satan providing all of his needs. When Satan leaves his body, all of this is immediately canceled and Nicolae becomes a shriveled, emaciated barely-living cadaver.
- The undead (both lazar and regular ones) from The Death Gate Cycle don't get tired, don't need to eat, drink, or breathe, can ignore most injuries that don't directly impair their functioning and can repair even those with a necromancer's help (lazar who were necromancers can repair themselves almost instantaneously, making them all but unstoppable). As such, if they want you dead, they can and will keep coming until you are. The lazar are also an unusually literal example of this trope, as their soul wants to escape into the afterlife but cannot, and its attempts to do so compel the body to wander or, if prevented from doing so (such as by being trapped in a small room) to incessantly pace. These creatures are literally in perpetual motion.
- Family Skeleton Mysteries: Sid the ambulatory skeleton doesn't need to eat or sleep to keep going, though being depressed does make it harder for him to hold himself together.
- Buffy the Vampire Slayer: Adam is one, thanks to his Uranium-235 core.
- The Jem'Hadar in Star Trek: Deep Space Nine are genetically engineered so that the only source of nourishment they need is Ketracel White, a narcotic which keeps them loyal and without which they die after going violently insane. On top of that, they are conditioned to be unwaveringly loyal (though this has proven to be slightly unreliable, hence the White as a secondary measure). And the occasional Jem'Hadar has a mutation causing them to not even need the White, meaning that nothing other than violent death can stop them.
- Sweet Home: In the first episode, monsters that have been on the rampage and frozen in the snow for months wake up as Hyun-su walks out of the building. Aside from Horror Hunger forcing some to feed compulsively, others don't seem to need any food at all.
- The serpent that guarded the Golden Fleece, which never slept or left the tree except when drugged.
- In Dungeons & Dragons:
- Constructs such as golems have no physical needs. The Warforged Mechanical Lifeforms in the Eberron setting are a partial example in that they don't need nourishment but do need a few hours of complete inactivity each day.
- Undead don't need food or rest, though some types have Horror Hungers that they need to indulge.
- Outsiders like angels and devils don't need food or sleep, although they might enjoy them anyway.
- Partially the case with the mantis-like desert-dwelling thri-kreen, but they do not need rest, and can function constantly. But they do need to eat and breathe.
- Elves do not sleep (in fact they cannot sleep - spells that magically put creatures to sleep do not work on them) and suffer no ill effects for it. However they are stated to need roughly 4 hours of trance-like meditation every day.
- Artifacts in Magic: The Gathering usually have this quality, as do a lot of undead. Phyrexians in particular are prone to combining the two.
- Role Master has the Black Reaper, an extremely powerful demon that is commonly used to guard items or places. Once disturbed, it will never stop pursuing the offender until he or she is dead. It is immortal and doesn't need food or air, and is never bored. When it follows it's soon-to-be victim, it will just walk underwater through oceans or use it's magic axe to tunnel through all but the hardest material.
- Vampires in Vampire: The Requiem need blood to awaken in the evening but not to function normally. In theory, one could be perfectly happy in a sun-proof room for as long as it can force itself to stay awake at dawn.
- One particular covenant of vampires, the Ordo Dracul, have a way to increase the amount of sustenance from the blood they drink, increasing to 1.5X what they get when they drink from humans and doubling blood drunk from vampires. Two such vampires can (canonically!) make infinite blood by feeding off of each other, becoming this trope. The downside is it leads to blood addiction and/or More Than Mind Control and/or Food Chain of Evil kicking in. So to keep its members from trying this the elders in the covenant seal all such vampires in steel boxes which they dump into the ocean, whereupon said vampires spend eternity feeding from each other. note
- In the Legend System, the feat By Will Sustained can produce this or The Determinator depending on whether it's taken by a monster or a player character. At level ten breathing and sleeping become optional.
- Red Markets mentions that one of the things that makes studying the Blight so maddening is the blatant disregard for thermodynamics shown by the Casualties it reanimates. There's also a survivor enclave that uses Casualties on treadmills to generate electricity.
- Generally not the case in Warhammer; most undead need necromantic magic to sustain themselves, and are destroyed if it's cut off, while vampires require blood. One notable exception, however, is Abhorash, vampiric founder of the Blood Dragons. In one of the biggest feats of badassery in the story, he defeated a dragon in single combat and drained it of blood. This had the side effect of permanently removing his need for blood, making him the sole creature in the setting with absolutely no need for any form of sustenance.
- Necromorphs in Dead Space neither need to eat, drink, sleep, nor breathe. Have fun! The Hunter has the added benefit of infinite biomass to regrow lost limbs, making it almost unstoppable.
- The Dahaka from Prince of Persia: Warrior Within fits the role.
- Dwarf Fortress actually has tags for these including [NOEXERT], [NO_EAT], [NO_DRINK], and [NO_SLEEP]. In-organic creatures like bronze colossi and iron men don't need any, while Goblins just don't need to eat or drink (due to the idea that all of them should die a violent death).
- Corprus infectees in Morrowind suffer massive, uncontrolled muscle growth, to the point where they can apparently survive by cutting off their own tumors and eating them.
- Alex Mercer and James Heller in the [PROTOTYPE] games are stated to have no need for food or rest and only absorb people to heal major wounds.
- Reapers in Mass Effect can operate a seemingly infinite amount of time without the resupplying other ships need constantly. This gives them a rather considerable advantage against everyone else. It's generally assumed that whatever it is they're using for fuel, it's based in technology beyond the understanding of their targets.
- Left 4 Dead hangs a dramatic lampshade regarding the Infected. One of the pieces of graffiti on a safe room reads:
They don't eat, they don't sleep, WHAT KEEPS THEM GOING?
- Robots in the Fallout games. By Fallout 4 it's been more than 200 years since the war that destroyed civilization, but you'll still find plenty of Mr Handies and Securitrons operating at full power despite a lack of access to any apparent fuel sources. Ghouls, despite being alive, are occasionally treated this way as well: there are multiple instances in the game where you'll encounter feral ghouls that have been trapped inside a room without a food source since the bombs fell, and they're still very active.
- Doomguy in DOOM (2016) and onward is a player equivalent of this. Canonically he does not need rest, food, or even hydration thanks to the enhancements in his body allowing him to subsist off of the essence he absorbs from the demons he slays. The result is a One-Man Army running on a perpetual Roaring Rampage of Revenge to slaughter Hell and its forces whenever they arise. He's so unstoppable and unceasing in his crusade that Hell itself fears his brutality.
- Touhou Project has Kaguya Houraisan and Fujiwara no Mokou, who drank an inmortality elixir that works by putting their bodies in a state of permanently perfect stasis and making the very concept of death not apply to them. As a result, they do not need any food. They do, however, still feel hunger and suffer after not eating for long enough.
- Robots in Kenshi, unlike every animal and sentient species in the world, don't need any food. This being a Survival Sandbox game, not needing any food and therefore not having to devote money, manpower and resources to feeding yourself is a major advantage.
- Erfworld: In the titular RPG-Mechanics Verse, the zombie-like Uncroaked and intelligent undead Decrypted have zero upkeep cost for their faction. Oddly, the latter still eat and drink, and are provided with what they need as if they had their usual upkeep cost (in the textual interludes, Parson tried Decrypted archon rations). Something outside the known forces of the world is evidently picking up the tab.
- After Act 5 Act 2 of Homestuck, the Peregrine Mendicant spends 3 years chasing Bec Noir across the chasm of space between worlds without either ever stopping, save for a very brief interlude.
- The Stand Still, Stay Silent variant of zombies has living beings that were infected 90 years ago still running around. Word of God is they do technically need to eat and drink, but can survive on extremely minimal nutrients if necessary.
- In El Goonish Shive, Nanase and Sarah discuss encountering wolves living in a sealed crypt and waiting by the door to eat someone despite there being nothing to eat or drink in such a place.
- The Order of the Stick: As one of The Undead, the Sorcerous Overlord lich Xykon doesn't need food, drink, air, or rest. The latter means he gets pretty bored lounging around in his conquered territories, because he's not interested in ruling and the RPG-Mechanics Verse only lets him spend eight hours a day Item Crafting.
- The wooden soldiers from Doraleous and Associates. Though they can be disabled with enough damage, their master need only command them to rise again and they will.
- The whole premise of the Rooster Teeth Animated Adventure The Snail Assassin.
- In the Friends at the Table series PARTIZAN, one of the antagonists is Motion, a machine god (or Divine) with the power to drive movement. It heads the Black Century, an elite unit of 100 soldiers and Humongous Mecha who serve 100-year terms, during which Motion keeps them alive and fighting no matter how much damage they take or how low they are on supplies. Troops nearing the end of their century tend to be just a few steps removed from corpses, but are not allowed to die until Motion releases them.
- In Steven Universe, the Gem monsters, much like the Gems themselves, require no sustenance to continuously project their Hard Light bodies and can live forever provided their gemstones are not shattered. Because of this, the Crystal Gems have to bubble their Gems to keep them in suspended animation when they "poof" them. Gems at least need sleep after long periods of heavy exertion, but the main gems apparently haven't needed to sleep before the second season episode "Chille Tid".