Universal Poison

""What a convenient world we live in. One medicine cures everything...""

- Adell's mom, Disgaea 2.

In Real Life, there are many types of poisons. Variations exist that will affect nearly any organ or system. Poisoning can manifest itself as nearly any symptom known to man. Different individuals and (especially) species are not affected by poison in the same way; chocolate and caffeine are toxic to dogs and cats, but relatively harmless to most humans. Capsaicin can seriously irritate human skin and mucous membranes, but is completely unnoticeable to birds. The dosage is also important, if you care whether the victim gets mildly nauseated or dies quickly. As Paracelsus pointed out, even life-sustaining substances become toxic in excessive amounts. Essentially, poison can be any substance that a particular body can't deal with at that particular dosage.

However, in fiction -- especially Video Games -- poison is treated as some sort of mysterious mass that saps the life force out of the poisoned one. There's one type of poisoning (not counting stronger versions of the usual), and any antidote will cure it. Usually presented as green, purple, or both, and optionally colors the victim in the same tone.

The default traits of poison are:

As a Standard Status Effect:
 * There is only one kind of poison in the world. All venomous creatures and poison-elemental spells use this same kind of poison.
 * While they come from many different places and are made out of vastly different materials, toxic waste, radioactive waste, chemical waste, sewer waste, heavy-duty pesticides, and even oil all cause the same kind of damage or condition, and usually look the same, being either green, purple, greyish, or brown, complete with a bubbling surface and sickly glow for the more colorful variants, despite the fact waste can assume many colors, textures, viscosities, and thicknesses, and usually is out of the range of Technicolor Science properties.
 * Poison is often the same thing as disease or sickness. Venomous creatures, gooey and/or acidic enemies, and poison-elemental spells will inflict the condition on you, but often times, so will attacks from rotting zombies, wild/rabid animals, and filthy creatures.
 * This universal poison has only one effect - it will slowly sap the life force out of any living creature inflicted by it, but will not hinder them in any other regard. This damage is caused at a constant rate, often a percentage of the victims total Hit Points, and is completely unaffected by things such as dosage or the body mass of the creature poisoned.
 * If there are multiple types of poison, the only difference will be the degree to which they harm the poisoned individual (e.g. reducing their HP by 5% or 10% every round).
 * It affects all living creatures equally regardless of physiology -- a human, dog, insect or dragon will all suffer the exact same symptoms. If a creature does resist a poison, it will resist all poison. That being said, sometimes things that should logically resist all poison, such as The Undead, golems, and robots, are perfectly susceptable -- especially if they just so happen to be Player Characters.
 * As there is only one type of poison in the world, there will obviously also be only one type of antidote. This antidote will work instantly when applied, and will usually be commonplace. (Though Cure-Alls will also work most of the time)
 * If there are multiple types of poison, there will still only be one type of Antidote.
 * There may be areas where the mere act of standing on a specific location will poison a character. In this case, it may inflict the status ailment, or it may deal damage per step or unit time. Often an item will exist to negate this effect.
 * Often, poison will not be lethal, despite being quite capable of bringing characters to the brink of death. Usually, it will drop to one hit point and stay there, though the poisoned status will remain.

Poison as an element: 
 * Poison will be classified as an elemental force of nature, on par with fire, water or electricity. If Functional Magic exists, there will often be an entire school of magic devoted to utilizing elemental poison.
 * If not used as a proper element, poison will be shoehorned into a miscellaneous damage type.
 * Poison is often damaging as an element towards earth, air, water, and/or plants, because it's generally perceived to be associated with decay and pollution of the natural world, even if it comes straight from the natural world itself (i.e. monsters). "Clean" elements such as water, air, and even holiness also tend to be very damaging towards poison elemental forces.

Both elemental and status effect poison: 
 * It is typically liquid or gelatinous in nature, and is usually green, purple, or orange in coloring (See also Technicolor Toxin for a complete list). It might also color any victims in the same tone. Bubbles of the same color may float over the afflicted character's head.
 * Acid is often mistakenly classified as a poison. Universal poison will almost always be highly corrosive. Although it is worth noting that the vast majority of acids also happen to be toxic, and in toxicology corrosion is a perfectly legitimate mechanism of action for a poison (bee venom, for example, is a type of poison that is acidic while wasp venom is a strong base). So there is some truth to this, just not to the extent normally portrayed.
 * In fiction, poison also tends to be highly corrosive when spilled (because it's wonderfully dramatic for the Big Damn Heroes to knock the poisoned goblet from the victim's hand in the nick of time and watch as the poisoned wine eats a hole through the banquet table.)
 * If Regen Hurts Zombie, poison does the opposite.

Sometimes a bottle or vial of the above substance is used as a trick powerup with negative, instead of positive, effects.

An Acceptable Break From Reality, as most players would not want to have dozens of remedies to sort through to handle the specific type of poison that one monster might inflict, especially if there are many other Standard Status Effects to carry cures for.

Literature

 * The Basilisk venom in Harry Potter. Poison from the Basilisk's fangs was a corrosive substance capable of destroying any magical or not magical object,.
 * Beyond all hope of recovery as well. Inanimate objects normally can be repaired with a quick spell. Not after they have Basilisk venom on them.
 * One wonders what Basilisk fangs are made of, and why Voldy didn't think to make one into a Horcrux...
 * Because Voldemort chooses his Horcrux for their sentimental value.

Video Games
"Hisui: So uh, just how does a Mechanoid get poisoned, anyway? Kunzite: It cannot be helped. I am constructed to be very similar to a human being. Hisui: Don't brag about it!"
 * In Pokémon, Poison is one of the 17 elemental types, and it includes some acid-based attacks (although the explicitly acid-based moves are also the only poison moves that cannot cause the Poison status effect). Poison-type Pokémon are immune to the poison status and take reduced damage from Poison-type attacks, while Steel-types are completely immune to both from Generation II onwards. There are two different types of poison status: regular "Poisoned" saps a set amount of damage (1/8th of max HP) every turn, and the "Toxic" effect that gradually increases in damage from 1/16th upwards every turn the affected Pokémon stays in battle.
 * And purple seems to be the color of choice for many Poison-types in these games.
 * In Generation V, poisoned Pokémon pulse purple (alliteration not intended).
 * Final Fantasy VII gives poison its own "-ra -ga" classification for use with its Powers as Programs magic system (and the chaining of passive abilities tied to it.)
 * Originally the elements in Tibia were Energy, Fire and Poison, with poison being the weaksauce one as a status ailment doing the least damage (though, it varied, Scorpion poison was pretty lethal, except...) and being the only ailement that was curable. A recent update added additional elements. Poison is still the weaksauce, though.
 * Diablo II, along with lightning, fire and ice. There may be some sources that deal direct Poison damage, but for the most part it's always a damage-over-time effect that has the neat bonus of preventing monsters from regenerating their health till it wears off.
 * Kingdom of Loathing generic poisons reduce your stats rather than deal damage, but are otherwise the same, right down to the anti-anti-antidote curing all of them.
 * The new raffle familiars in Kingdom of Loathing play this one straight, as their poison attack does continual damage to your enemies every combat round.
 * Pufferfish venom can damage the player, but also be used by the player with the right item. The damage increases exponentially each combat round and is the only way to reliably kill the hardest (purely optional) bosses in the game. Cannot be cured but wears off outside of combat.
 * "Toad in the Hole" is a fourth kind of poison, that is also cured by the anti-anti-antidote - the toad venom cuts your Hit Points in half, then does steadily decreasing damage each turn thereafter.
 * Technically this means the game has more than one kind of poison, but most do fit the trope.
 * Invoked by the green BRICKO brick, whose description explains that all poisonous things are green.
 * In World of Warcraft poison is classed as 'nature damage' along with diseases (and some druid spells.) Monsters such as snakes, tainted elementals, and enemy rogues will put Poison on you; the most common kind is a Damage-Over-Time effect that surrounds you with a green cloud or turns you green. Interestingly, although there are many types of poisons, the antidote is always universal -- any cleansing spell that dispels poison will dispel all types of poison.
 * Usually. Kind of a tricky issue mechanically, since although Poison and Disease are both nature damage, the same spells won't always cure them. Poison, Disease, Magic, and Curse effects used to all require different spells to get rid of them, and not all healing classes had all of the dispels. So a healing druid would do a questline to cure a poisoned NPC, and at the end of it would be taught a spell that cures Disease, but not Poison! And some of the dispels were given to classes that aren't normally healers at all -- Mages (but not warlocks, who deal primarily in curses) had the Decurse spell. Recent changes to the healing classes have ensured that for the most part, all types of healers will have a spell that will take care of all debuffs.
 * The damage type of all poisons will be nature, but not all poisons do damage. Rogue classes have access to a variety of poisons with other effects, like reducing movement speed, dulling an enemy caster's mind to reduce cast speed, reduce healing taken, et cetera. Of course, just how the poisons work when put on a blunt weapon like a mace instead of a weapon actually designed to penetrate skin like a dagger is the question...
 * Maces tend to break and pulverize the flesh, leaving wounds that resemble ground beef and spaghetti sauce nicely seasoned with bone spurs. They would have little difficulty mixing poison into the bloodstream. Furthermore, many poisons in real life can be absorbed via surface skin contact (dart frog venom, for instance), so in some cases breaking the skin may not even be necessary.
 * Except its unlikeable for blunt weapon to tear through even leather armor.
 * Etrian Odyssey, in which the Alchemist has a poison ability, which doesn't really fit into the general fire/ice/volt/physical attacks pattern.
 * There's a variant in Prince of Persia where poison looks like a Healing Potion, but it's oddly coloured.
 * The SNES version has another poison that looks exactly like a life upgrade, but kills the Prince instantly.
 * Mega Man Battle Network had poison panels, which inexplicably hurt you just by standing on them. Then there's the Poison Pharaoh, which poisoned you... and the antidote was destroying him.
 * In Maple Story, the magic system is separated into Fire, Poison, Ice, Lighting, and Holy.
 * Poison was also considered an element in Magical Vacation, along with a whole bunch of other weird elements like Beauty, Sword, and Bug.
 * Valkyrie Profile has six elements, of which one is Earth, which has a chance of randomly poisoning enemies.
 * Retro Mud has Toxic magic on the balancing scale or magical energy. It balances with Illusion magic, and overuse of either strengthens the other.
 * Toxic is also a (fairly rare) damage type in City of Heroes (along with Smashing, Lethal, Fire, Cold, Energy, Negative Energy, and Psionic
 * The original Dragon Quest had poisonous swamp tiles which would cost the hero 1 HP per step. Erdrick's Armor would negate them. Later entries in the series added the status effect.
 * Runescape has regular poison, stronger poison and a super poison, used on weapons. Also a special type of poison made of a fish called Karambwan. The Karambwam cannot be cured through normal anti-poison, but the first three are just stronger versions of eachother.
 * Resident Evil has several different types of enemies to poison you, but the same magical Blue Herb cures them all. At least partially justified in that all the monsters were affected by the T-Virus and so the poisons would all presumably be similar.
 * However, there are some exceptions to the rule that appear from time to time where the poison is particularly powerful that not even the blue herbs can have any chance to heal them. Examples include poison inflicted from Yawn's bite (as in the giant snake slithering all over the mansion) which can only be treated by a serum found in another room (which you either have to use on a survivor or yourself) in the first game, or Nosferatu's toxic plume of gas in Code Veronica which was specifically designed by Alexia to be immune to the blue herbs and also requires its own special serum (which Chris must give to Claire if she's infected while fighting Nosferatu).
 * Yet another poison-like status occurs when Jill is infected by Nemesis in Resident Evil 3 Nemesis. Carlos must travel to an Abandoned Hospital to find an antidote.
 * The Elder Scrolls II: Daggerfall is very bizarre in this respect. There are many types of diseases with different carriers, regions, and effects throughout the game world that anyone who is not entirely immune will come down with at one point or another, but there is only one type of poison throughout the Illiac Bay.
 * Somewhat confusingly, this means you could make a poison-based spell that caused paralysis, lost of magic points, or whatever, but this was in addition to the generic Universal Poison.
 * The Elder Scrolls IV: Oblivion changes the poison system so that you can use alchemy to make your own poisons with varying effects. You can make poisons that simply damage health, poisons of fatigue, poisons that cause paralysis, etc. However, a universal antidote cures any of them and the reptilian Argonians are immune to all poisons.
 * There is, in vanilla Oblivion, one type of "poisoned apple" whose effect, though called Deadly Poison, isn't considered by the game mechanics to be a poison. This means that anyone who eats it, regardless of poison resistance or immunity (barring being able to heal really quick) is poisoned and will die--even the player.
 * The Elder Scrolls V: Skyrim Uses a system similar to that of Oblivion. For example, there are a few levels of basic poison, poisons which reduce your resistance to specific elements at varying amounts, and so on.
 * Command and Conquer Generals fits this trope perfectly with its toxin, called 'anthrax' in-game but acting wholly unlike real-world anthrax, poisoning everything almost immediately. In order of strength, the three forms are green, blue, and purple.
 * Complete with Alpha, Beta, Gamma designations!
 * In Wizardry series levels of poisoning differ, but it's the same Status Effect. Before Wizardry 8 there was also separate Poison resistance.
 * In Age of Wonders Poison is both damage type flag and stats-weakening (but not life-sapping) Status Effect, so unit can be hit by Poison-only type attack and suffer Hit Points damage, but then becomes "Poisoned" only if it was also hit on second resistance check.
 * Battle for Wesnoth's poison affects every single unit type in roughly the same way, with a few minor exceptions - the undead and mechanical units are entirely unaffected, trolls and other regenerating units can heal the poison, and units with the Healthy trait take less damage from it. Everyone else, no exceptions, takes 8 HP damage per turn until they reach 1 HP remaining, or are healed or killed.
 * The poison = acid thing is justified in the Gundam RPG MS Saga, in which corrosives are the only source of the "poison" status effect, as it affects the Humongous Mecha rather than the pilot.
 * In the old black & white Macintosh RPG Shadowkeep, spider and scorpion venom require different antidotes to cure, and you can have different amounts of both flowing through your veins.
 * Guild Wars has poison as a "condition", a Standard Status Effect, which drains 8 HP per second. It turns your health bar green, produces a sickly cloud of green gas around your character, and is functionally identical to another condition known as "disease", except that disease can also spread to other creatures of the same species. Both conditions can affect any "fleshy" creature in the game, and both can be cured by any skill which removes conditions.
 * Lampshaded by Tales of Hearts in a Victory Pose, if Kunzite is poisoned in combat and Hisui is present.


 * Poison in Dokapon Kingdom does your level in damage each round. Z Plague, which is transmitted by chimpies, does double that.
 * The gradual damage effect is inverted in Half Life 2 "Poison Headcrabs", which do a huge amount of damage straightaway (dropping you to 1 health point, and medkits do not return this damage) which immediately begins to heal back (to what you were at before being poisoned), representing your HEV suit "administering antivenom". So, essentially harmless - unless they manage to get you in the middle of a battle. Poison headcrabs themselves are not capable of killing you, even multiple ones. They are often carried on the back of a larger zombie who first throws three or four of them one at a time, then charges you while you're poisoned to one point. He is capable of removing that last hit point, as well as any others you may have handy.
 * Similar to Diablo 2, being poisoned in Hellgate:London prevents an character (including enemies) from regenerating its HP. It occurs as a randomly generated effect when a character takes damage from a Toxic weapon / spell.
 * Metal Gear is the perfect example. There's one thing that can poison you (getting stung by a scorpion in the desert) and one item that can cure you (the Antidote, and that's exactly what it's called), which thankfully has unlimited doses.
 * Curous example is Dark Corners of the Earth. There is only one type of enemy which can poison you, and you meet them only twice in the game (and the first time, you don't have any weapons, so you should just run from them like hell). However, the antidotes, which are the only item that can cure poison damage, are very abundant.
 * In Star Wars Knights of the Old Republic, there is just one type of poison damage, regardless of whether the attack comes from weaponized chemicals, ancient blades, venomous beasts, or force powers.
 * White Pikmin from Pikmin 2 are not only immune to poison, but they can also release toxins and damage enemies when consumed.
 * The latest version of Dwarf Fortress introduces "syndromes" which replace and... enhance the previous Universal Poison and vastly avert the trope. They are defined as one or more different effects, including nausea, dizziness, bleeding, paralysis, necrosis and many others, any of which can affect one or more specific body parts or systems. They can be given an intensity of effect, chance of resistance, given lengths of time for onset, peak and recovery time. The method of contagion can be defined as via injection (bite), inhalation or on contact and creatures can breathe, spit, ooze, bleed or release a constant cloud of their poison. Unless a recovery time is specified, once a creature contracts a syndrome, it's not curable. Forgotten Beasts each get a random syndrome with one or more effects. This usually results in much Fun.
 * The trope is also subverted with the new medical system. A doctor can sometimes "cure" a dwarf of a syndrome by removing the infected body part before it causes any further side effects.
 * A story in the forums told of a military squad getting a syndrome that caused their skin and eyes to rot away, but after surgery to remove the rotten tissue (preventing further rot or death by infection) and some presumably liberal use of bandages, his dwarves went back on duty. The syndrome also paralyzed parts of their nervous system, which left them unable to feel pain, so the fact they no longer had any skin didn't bother them.
 * Sword of Vermillion uses this trope straight most of the time, except in one event where the main character is affected by a poison that is much stronger than usual and resists all the standard cures, leading to a Find the Cure scenario.
 * Spiral Knights includes a standard poison effect that can be inflicted by anything from zombies to robots to rabid wolvers and affects all players and monster types the same, but the actual effects are a bit off standard. It deals no damage, but it makes the victim take more damage, deal out less, and prevents them from receiving healing sources.
 * Legend of Legaia has two varieties of poison: Venom and Toxic, with Toxic being twice as strong.
 * The sequel also has two types of poisons: the first one being a regular poison that does damage per turn based on percentage, while the second and more dangerous one has a secondary effect that nullifies all healing done to the affected character until the poison is cured.
 * Ys I has the Evil Ring which either drains your HP or kills you instantly, depending on the version, unless you equip the Blue Necklace first. Darm Tower later has the "Devil's Corridor" where evil music drains your HP. Starting with Ys IV: Mask of the Sun the series featured poison as a status effect.
 * The Eggplant that drains your vitality in Wonder Boy and Adventure Island.
 * In Nethack poison isn't a status effect, but deals a certain amount of damage once and immediately, with a chance of reducing the victim's strength attribute. Additionally, poisoned weapons and pit traps with poisoned spikes have a chance of instantly killing anything that doesn't have poison immunity. Lost strength can be recovered by several different magical means.
 * Pathways into Darkness has a poison status effect, and an alien MacGuffin that drains your vitality unless kept in a lead box.
 * In the Find Mii game built into the 3DS, characters with purple shirts use poison magic on enemies. It does 1 damage per turn.
 * In Chrono Trigger, Poison is used in much the same way as it is in games like Final Fantasy. The interesting thing about it is that Robo can be poisoned as easily as any of the characters that actually have organic systems to poison.
 * In Chrono Cross, poison takes off 1 HP for every stamina point an ally or enemy uses. Similarly to Robo in Chrono Trigger, Mojo (a voodoo doll), Grobyc (a cyborg), Skelly (a skeleton), and several plant people can be poisoned as easily as everyone else.
 * Athena has a HP-draining poison effect which can be inflicted by spiders, scorpions or poison potions.
 * Global Agenda's medic has poison that's both a debuff and a DoT, and targets anything. Robots? Check. Consoles you have to destroy? Check. Even better, it appears to deploy as a spray that makes its way through armor that selectively targets enemies. There are also pools of this stuff in the open world, "explained" as irradiated water...

Tabletop Games
"*On mountain giants* Whatever you use, use a lot of it."
 * There were dozens of different poisons throughout the various Dungeons and Dragons sourcebooks from the start, with different effects. In 3rd Edition none of them even do direct Hit Point damage. The damage is dealt instead to the character's attributes (Strength, Dexterity, Constitution, Intelligence, Wisdom, or Charisma), and the type and amount of damage are different for each poison. However, they generally affected all creatures the same way, the exceptions being creatures that were immune to poison (and who were thus immune to all poison), and poisons that specifically affected only certain types of creatures. The few exceptions to those exceptions were gone by 3.5. (3rd Edition druids, for example, could become immune to "natural" poisons--but not mineral poisons. In 3.5, they simply became immune to poison.)
 * The trope is now played completely straight, however, in 4th Edition. Poison is now just another damage type, and is usually paired with the system's ongoing damage mechanic. These can get a bit strange: A green dragon's poison lets it control your mind, while a Couatl's poison also does radiant damage.
 * In the Pathfinder rules set, which is essentially a debugging of 3.5 by another company as opposed to 4th editions ground-up rebuild, poisons are still effects that do stat damage over varying amounts of time and require certain delivery methods (contact, injury, and ingestion, though there is some overlap). They do affect most creatures the same way regardless of their type, mostly to avoid making the rulebook into a medical diagnosis sheet. However, the only creatures that are really immune to poison are either things with no anatomy to affect, like elementals and undead, or innately magical creatures that would need these immunities to survive their inimical environments, like Devils. Kind of hard to lord it over the tormented souls when you can't breath the atmosphere.
 * Lampshaded in the Warhammer Fantasy Battle rulebook, which states this trope is in use for simplicity's sake. It also notes that there are exotic poisons for exotic creatures, such as Holy Water for The Undead, which poisoner is assumed to have access to and can use when fighting such opponents.
 * Somewhat averted in the Warhammer Fantasy Roleplay bestiary, which includes in-universe commentary from a Skaven assassin which consists solely of the best poison to use on each of the entries. This involves as simple things as arsenic (fellow skaven) to ground glass and nightshade (ogres), to warpstone powder (The Undead) or holy water (daemons). Or, in one case:


 * In GURPS all (normal) poisons inflict toxic damage, and some cause damage to ability scores or inflict status ailments. However, curing a poison does require knowing what kind it is unless you have magic or the like.
 * And "toxic" as a damage type isn't actually restricted to poisons; it's more like a catch-all term for "cellular damage" done by e.g. poison, disease, radiation etc.

Webcomics

 * Parodied in this Adventurers comic.

Real Life

 * There lives a certain species of sea slug which bypasses this trope completely. It packs somewhere around a hundred different toxins and uses them all simultaneously, essentially making sure that no matter what it's attacking, it's going to die. This also practically ensures that none of its preferred choices of prey, nor any of its potential predators, ever develops a resistance to its venom.
 * The page quote from Paracelsus is actually very true: almost any substance is dangerous with appropriate dosage. On the other hand, almost any substance is in some way beneficial (or at least harmless) with appropriate dosage.
 * This extends all the way to the most lethal poison known to man: Botulinum toxin. Not only is it marketed as Botox, but it has a number of other oddball medical uses involving paralyzing muscle tissue. In really, really low doses, obviously, since nanograms of the stuff can kill you.
 * Chlorine gas...sort of. It's not technically poisonous, it "merely" reacts with water to form hydrochloric acid. Any creature which has moisture somewhere on its body will find it becoming acidic when exposed to chlorine gas.
 * Cyanide is probably the closest thing to a universal toxin, as it imitates the shape of oxygen and sticks permanently to the protein turbine in mitochondria that processes oxygen to water, blocking it up. In other words, cyanide is deadly to every organism that respires using oxygen.
 * Likewise arsenic, which interferes with the ADP/ATP aspect of many chemical cycles in nearly every metabolic organism in existence. Recent discovery of a bacterium that could not only withstand high doses of the stuff, but even appeared to actually use it in its DNA (in place of its chemical cousin, phosphorous) rocked the scientific world.
 * Radiation- it doesn't matter what it is you're targeting, enough radiation will kill it. Of course, tolerance for radiation varies considerably among different organisms- small insects can withstand doses a hundred times greater than humans. While radiation is something all organisms must deal with (together with oxygen it causes more DNA lesions in a day to the average human than there are grains of sand in the world), a large enough dose will overwhelm an organism's capacity to regenerate.