Kim: How much is it?
Drakken: Is that bad?
Ann: It could be.
Let's face it, some characters are pretty damn hot. Other characters may have raging hot passion. But in this trope's case, we find fictional creatures that are literally Hot-Blooded (or anything that's close enough to blood).
This type of being usually has an implication (or at least a possibility) of a temperature difference that's caused by metabolism-based weirdness. This makes some sense, as there are several organisms in Real Life that have an average body temperature that's higher than the human average.
Characters that can play with fire tend to exhibit this trope, along with many fire-related monsters like dragons, salamanders, and fire-related familiars. Lava beasts, fire elementals, and other creatures that actually made of some heat related substance are another trope altogether.
- The Titans of Attack on Titan have extremely high body temperatures, which appears to increase along with their size. The Colossal Titan radiates superheated steam thanks to its lack of skin, and another Titan, twice the size of the Colossal, is so hot that it causes nearby vegetation to combust.
- JoJo's Bizarre Adventure:
- The Pillar Men from Battle Tendency have each mastered a type of fighting style called "Mode", where they freely transfigure their own bodies to emulate Elemental Powers. Esidisi's Mode is Heat Control, which entails heating his blood to 500 degrees Celsius (or 932 degrees Fahrenheit) then extending his blood vessels from his body and injecting his blood into an opponent. The results are just as horrifying as they should be.
- A lesser example would be Robert E.O. Speedwagon in Phantom Blood. It's never really explained how or why, but Speedwagon is so hot-blooded that he could melt Zeppeli's frozen arm just by holding it to his chest for a minute. Unfortunately, his hot blood makes him unable to use Hamon Techniques.
- In Kill la Kill, Ryuko is normally simply Hot-Blooded, but when she finally confronts her father's murderer her rage reaches a boiling point. That is to say, her blood is literally seen to boil, driving Senketsu into a frenzy.
- Shishio from Rurouni Kenshin was shot in the head and lit on fire before being left for dead. The fire left him disfigured, and all of his sweat glands were destroyed. As such, he has incredibly high body temperature, which (apparently) grants him almost superhuman speed and strength. The downside is that he can only fight for about fifteen minutes before the heat buildup kills him.
- In PS238, Suzi has an internal body temperature which can melt lead, which appears to stem from her radioactive nature. Incidents when she loses her temper are explained as "gas leaks".
- Runaways has a variation; while it is unknown if Karolina's Majesdanian blood is especially hot, it is supercharged with solar energy, a fact that the vampire Topher learns the hard way when he tries to feed on her.
- Supergirl's blood is burning-hot during her Red Lantern tenure in Red Daughter of Krypton. This is true of Red Lanterns in general, as the Red Rings' energy replaces their blood. As such, the removal of a Red Ring from their host would, under the majority of circumstances, result in their death.
- However, it may also be true of Kryptonians in general, at least under a yellow sun. During a story where Superman was deathly ill due to being attacked by a Kryptonite-bearing nanobot and a number of heroes needed to enter his body to save him, the ones who were vulnerable to such things were warned that his blood was hot enough to turn a human into grease in his bloodstream if their suits ruptured. This is probably due to Kryptonian blood being charged with solar energy, as shown when Superman gets bitten by Dracula in another story — the solar-charged blood plus the vampire's weakness to sunlight makes for an explosive result.
- Red Hulk gets hotter the madder he gets. Get him angry enough and enemies who touch him can be burned. He can even melt metal with his bare skin.
- Wonder Woman (1987): Medusa's blood steams, and the pool of blood from her decapitation gets hotter rather than cooler until Pegasus is reborn from it.
- In The Butcher Bird, Kaneki displays a much-higher-than-usual body temperature, and it increases as he gets angrier. His incomplete kakuja runs even hotter, to the point that it boils his own rinkaku into Deadly Gas.
- The Cut of Your Love Never Hurts, Baby: An inversion is deconstructed with Elsa. Not only is her body abnormally cold because of her ice powers, but she can't have children because of her body temperature. This comes with being An Ice Person and is a way for nature to prevent too many people with ice powers from existing at once.
- In DNMC, D'Arg's blood is used as fuel for his Flaming Swords due to the Fire Dust infused into his body.
- In Earthsong9405's Infected AU Zombie Fic, Twilight Sparkle was bitten years ago but didn't turn infected. The bite did, however, raise her body temperature and metabolism.
- Inverted in Love Worth Waiting For. Elsa was born with a very low body temperature. When she was an infant, her parents feared that she was ill because she was so pale and cold to the touch.
- In Pokémon Reset Bloodlines, James notes that Red has an unusually high body temperature when they shake hands.
- Downplayed in The Touch of Green Fire. Shego's plasma powers cause her to have a body temperature that's five degrees above the average. She also has a higher blood pressure than normal.
- In The Chronicles of Amber, denizens of the Courts of Chaos bleed fire under certain circumstances. The Merlin Cycle, whose viewpoint character is from the Courts, goes into more detail: certain Shadows react to the blood of Chaos, causing it to ignite upon contact with the air. When it's actually in the body, however, their blood is fluid no matter where they are.
- The Marat in Codex Alera are slightly warmer than humans. This is important in the first book, when one is trying to sneak into a forest guarded by creatures who see in infrared.
- Anyone in Eden Green whose needle symbiote takes over their body completely begins to exhibit elevated body temperature, immediately noticeable to non-infected people.
- The "vampires" of I Am Legend are humans with a disease that (among other things) sends the body into overdrive. They run a fever of about 103 Fahrenheit as a baseline.
- In the Inheritance Cycle, dragon blood is described as being roughly the same temperature and consistency as boiling tar.
- Sauron himself in The Lord of the Rings. The reason why his ring was glowing on his hand was because he was inhumanly hot.
- In a novel based on Magic: The Gathering, a Black-aligned vampire is set to fight a Red-aligned Geomancer in arena-style combat. The vampire manages to evade the torrents of stone and dirt, sink his fangs into the mage's neck and begins draining him dry... at which point the Geomancer turns his own blood into lava. Cue burning vampire.
- Simes in Sime Gen have a body temperature noticeably higher than that of Gens and children. This incidentally means they don't get sick as often as many germs can't tolerate the higher temperature.
- A Song of Ice and Fire:
- Dragons do this. In fact, wound them and leave the weapon behind, and it may start to glow with the heat depending on how high quality the iron or steel is. Bronze and copper are likely to fare worse and could well start to turn molten if left too long (and goodness knows if they can give the poor dragon blood poisoning or not). Good luck trying to play vet, though.
- Befitting a priestess of R'hllor, Melisandre is not affected by cold, and her body gives off noticeable heat.
- In The Sookie Stackhouse Mysteries, werewolves and other shifters are mentioned several times time as "running hotter" than their human counterparts.
- Werewolves in The Twilight Saga. Perhaps that's why they so rarely wear shirts.
- In Wings of Fire, Peril has twice as much fire as an average dragon, due to parasitically absorbing the fire of her (deceased) twin brother in the egg. Thus, she's burning hot to the touch, glows slightly in the dark, and has to sleep in a special room to avoid burning things around her. Her love interest, Clay, is notably more resistant to fire than most dragons, and one of the few capable of touching her without being hurt. Her Not Quite Dead twin brother, Sky, ends up being an inversion — he can't breathe fire and is cooler to the touch than most dragons.
- In Farscape, Scarrans are extremely hot and can project this heat as a weapon. Compare with Sebacceans, who are colder than humans and vulnerable to hot temperatures. Scorpius, being a hybrid of both races, needs cooling rods implanted in his head to survive.
- Marcos Diaz/Eclipse in The Gifted (2017). His blood glows, and when enough of it is spilled in a car, the car explodes. A member of the Morlocks has similar blood, and another mutant's blood melts through solid objects (although that may have been acid blood instead).
- In the Supernatural Season 4 finale "Lucifer Rising", Sam Winchester is said to have reached a body temperature of 150F (65C) when he was killing Lilith, courtesy of the demon blood he was using.
- True Blood has its werewolves.
Alcide: We run hot.
- Foreigner's "Hot-Blooded", with the singer saying he's got "a fever of 103."
- Inverted in "My Angel is the Centerfold" ("My blood runs cold—my memory has just been sold...")
- Dungeons & Dragons:
- The Remorhaz, a massive centipede-like creature that lives in glaciers, is hot enough that nonmagical metal weapons melt on contact and it can dig through the ice by melting a tunnel with its body heat. If it swallows you, it's instant death (in 2nd Edition) or a massive amount of fire damage thanks to its super-heated.
- Salamanders and Azers (metallic dwarf-like beings from the Elemental Plane of Fire) have bodies that are so hot that they can cause paper and wood to burst into flames just by touching them and heat their metal weapons so that they inflict extra fire damage on a hit. It's never really explained how this incredible heat doesn't cause their weapons to soften to the point of uselessness, but it's probably because they're magical.
- The Path of the Storm barbarian from Xanathar's Guide to Everything desert variant allows barbarians to take it to become so hot that enemies near them take fire damage just from their proximity (sadly it's so weak that it's practically useless) and set unattended objects on fire just by touching them.
- Pathfinder has Xotani, a gigantic worm whose title is the Firebleeder. Dealing too much damage to it in one attack (read: an amount large enough to actually harm it) triggers the equivalent of a flamethrower as burning blood sprays from the wound.
- Psionics: The Next Stage in Human Evolution features a somewhat realistic example of how this would play out in real life. The pyrokinetic ability Temper, Temper, Temperature can be used to raise the body temperature of living things. Raise it enough and they'll die from boiling in their own skin.
- Warhammer 40,000 has the Avatar of Khaine, which has molten iron running through its veins. It's also Wreathed in Flames.
- Warhammer Fantasy Roleplay: One of the Mutations that can be inflicted by exposure to Chaos transforms the victim's blood into molten metal or pure fire. This can be a case of Cursed with Awesome, as the "blood" generally isn't harmful to the mutant but can damage anyone who injures them.
- Karlach from Baldur's Gate III starts out with an infernal machine of Avernus in place of her heart. Until it's repaired, she Can't Have Sex, Ever, or even a hug, because she'd burn her partner. (It also means that if vampire spawn Astarion tries to bite her, he'll get a painful burn for his troubles, and that remains the case even if he ascend to a full-fledged vampire.)
- In Dota 2, Huskar's trip to the Nothl Realm changed his physiology, making his blood highly volatile. He can use this blood to light his javelins on fire, inflicting Damage Over Time at the cost of being Cast from Hit Points.
- KanColle: Kaga runs very hot, to the point that she's occasionally used as a makeshift heater. The real-life Kaga had a similar problem; her exhaust system couldn't get rid of all excess heat, which built up in the flight deck and some of the crew quarters.
- Monster Hunter:
- Monster Hunter 3 (Tri):
- Deviljho's immense body heat makes it spew smoky black Dragon energy out of the wounds on its back when enraged. Unfortunately for the Deviljho, this means it has to eat almost constantly, to the point that it'll drive entire ecosystems to extinction and eat parts of itself just to stay alive.
- Dire Miralis in 3 Ultimate is so superheated that its body boils oceans and decimates their ecosystem.
- Monster Hunter Generations Ultimate: Bloodbath Diablos' rage towards humans means that its blood will literally start to boil once it's sufficiently enraged. It puts this to good use, too, as it'll emit a damaging burst of superheated steam whenever it erupts from the ground.
- Monster Hunter: World: Bazelgeuse is a Flying Wyvern that can use its own bodily fluids to create grenades, which it then goes on bombing runs with and blows its prey to smithereens. When enraged, these grenades will glow red and explode upon touching the ground, rather than exploding when something hits them. The Seething variant is so angry that its grenades are constantly red... instead, they become white-hot Sticky Bombs when enraged.
- Monster Hunter 3 (Tri):
- Noita: Some fire-based enemies bleed lava on being attacked, which will cause massive damage on contact with other creatures. This is especially prevalent in the Hell biome.
- Nuclear Throne: The Boiling Veins mutation prevents fire and explosion damage from reducing your HP below 4. It's depicted as their blood literally burning.
- Many Fire-typed Pokémon are described as having a flame-producing sac or other such organs in their bodies. Some Pokémon like Magcargo and Heatran literally have magma for blood.
- In Resident Evil – Code: Veronica, Alexia Ashford's main method of attack is slinging her blood at her foes, which combusts on contact with the air. Another host of T-Veronica, Manuela Hidalgo from Resident Evil: The Darkside Chronicles, shows these same powers, though she's not nearly as evil as Alexia. It can be assumed that the fire-based attacks of her father Javier's V-Complex form run on the same principal as well, as they also spring from Veronica.
- The various Mutons in XCOM: Enemy Unknown and XCOM 2 are noted to have bodies that remain warm hours after their deaths. Dr. Tygan mentions that this makes them quite disconcerting to dissect.