Horror

Horror is a catch-all creature type used for horrible, black-aligned fiends and beings that defy normal descriptions. Horrors originate from different sources such as nightmares, scientific experimentations and hellish planes. The first creature to bear the type was Cosmic Horror in Legends. Many cards received the Horror type retroactively in the Grand Creature Type Update. Notable creatures from early sets, like Abomination and Hell's Caretaker retroactively became Horrors.

Horrors don't have a prevalent ability, but most of their abilities do some sort of harm to the controller of the Horror. Many of them also have some kind of evasion.

Between 1995 and the fall of 2002, Horrors replaced Demons as the black iconic creature.

Amonkhet
The Desert Lands of Amonkhet are not only inhabited by undead abominations, but also horrors who prey on those that dare live outside the Hekma. Some of the creatures rival even the gods in size.

Several of these, like the Grim Strider and the Scrounger of Souls, have elongated forelimbs and a mask-like bone plate instead of a face with a glowing rhombus of light modeled after an eye in its center. Other Horrors are spawned from enchantments or are warped inhabitants of the plane, like the Wasp of the Bitter End.

Arcavios
One of the Oriq’s most powerful tools is the Mage Hunter, a vile monstrosity created to seek out and snuff out the arcane.

Dominaria

 * A powerful Cosmic Horror was summoned by the dark planeswalker Geyadrone Dihada to sack the city of Sedouris on Corondor after Sol'Kanar the Swamp King had held the city under siege for five years.
 * The Ice Age was plagued by Krovikan Horror</c>s and Void Maw</c>s.
 * Another Cosmic Horror</c> was trapped by Shauku in her underground lair, the Caverns of Despair</c>. The captive Horror summoned a Falling Star</c> and destroyed Shauku's lair.
 * Urborg was one of the regions of Dominaria with the most concentrated amounts of black mana in modern times. It attracted such creatures as the Fetid Horror</c>, the Urborg Mindsucker</c> and the Abyssal Gatekeeper</c>. Some of these may have been of Phyrexian origin.
 * Greel, Mind Raker</c> was a strange demon controlled by the Keldons during the Keldon invasion of Jamuraa.
 * Dementia casters like Chainer, Dementia Master</c> and other members of the Cabal on Otaria have the unique ability to summon horrors from their personal "dementia space," a place populated with the caster's greatest fears and all beings they have killed. These are represented as Nightmare Horrors, and in Torment all had the mechanical connection of removing other cards from the game when they entered the battlefield and returning them when they left the battlefield, or in the case of Laquatus's Champion</c> and Soul Scourge</c> causing an opponent to lose an amount of life when that creature came into play and gain that same amount of life when that creature left the battlefield. Time Spiral's Faceless Devourer</c> is a reference to this.
 * Odyssey features a white Angel Horror in form of Wayward Angel</c>, which can change into black when Threshold is active. This ability is also seen in the "Possessed" creatures cycle from Torment ( Possessed Nomad</c>, Possessed Aven</c>, Possessed Barbarian</c> and Possessed Centaur</c>) which have the activated ability to destroy creatures of their previous color.

Grixis

 * Alara was a whole world before the Sundering broke it into the five Shards. The shard Grixis became a vast wasteland dominated by horrors, demons, necromancers and undead. The event known as the Conflux has recently reunited the shards, causing much chaos and mayhem to their respective residents. Grixis horrors include the Shambling Remains</c> and the Nemesis of Reason</c>.

Innistrad

 * The "horror block" of Innistrad of course harbors several Horrors. Some, like <c>Ludevic's Abomination</c>are created by men, some like <c>Unholy Fiend</c> are not. A large variety of these are blue aligned zombies, while others are normal creatures that are transformed into horrors, perhaps to accent the unnatural creation. In recent times, as a consequence of Emrakul's corruption, a variety of horrors have appeared in other colors of mana, such as the red aligned <c>Scourge Wolf</c> and the green <c>Kessig Dire Swine</c>, the transition between organic creatures and full-blown Eldrazi.

Ixalan
Indescribable creatures of nightmare lurk in the ruins and dark places of Ixalan. Many are thought to be the corrupted remnants of the life energy and brilliant light left behind in places the Sun Empire has abandoned. Such creatures include a monster that lurks in the darkness of the jungle and feeds on the blood of mammals and dinosaurs, called the chupacabra. It is stealthy and elusive, known more by the blood-drained prey it leaves behind than by actual physical sightings (<c>Lurking Chupacabra</c>, <c>Ravenous Chupacabra</c>).

Mercadia

 * Horror mercenaries were to be found within and without the Cateran Guild of Mercadia, like the <c>Cateran Overlord</c> and the <c>Misshapen Fiend</c>.

Phyrexia

 * Phyrexian horrors, among them the <c>Phyrexian Negator</c> first showed up in full force in Dominaria during the Brothers' War of the Artifacts Cycle.
 * Urborg was the first location where the horrors from the vats of Phyrexia revealed themselves anew, the first being the brothers <c>Morinfen</c> and <c>Gallowbraid</c>.
 * Again at Urborg, the Phyrexian Invasion of Dominaria was led by <c>Tsabo Tavoc</c> and accompanying horrors.
 * From early on horrors, like <c>Greater Harvester</c> appeared on Mirrodin. Later, many more were featured in the takeover of Mirrodin, and the creation of New Phyrexia.
 * Carriers are related to Phyrexian Horrors.

Rath

 * When the Dauthi of Rath were trapped within the "Shadows", the extraplanar space between Rath and Dominaria, they were left in an incorporeal state. They were unable to communicate with people on either plane, yet able to see into both the Dominarian reality and that of Rath. This predicament led the Dauthi to lose their sanity, and some of them manifested as horrors (<c>Dauthi Horror</c>).

Ravnica
Ravnica has several kinds of horrors, most creations of one of the more unsavory guilds. The Dimir employ Horrors like the <c>Abyssal Nocturnus</c>, the <c>Dinrova Horror</c>, the <c>Consuming Aberration</c> and <c>Horror of the Dim</c>, who are created from a combination of necromancy and mind magic with the intend to guard their secrets. The Orzhov use Horrors to collect their debts from the unguilded by sending them into their quarters to collect their souls (<c>Slum Reaper</c>). The Rakdos cryptwitches employ their own brand of Horror, like the <c>Cryptborn Horror</c>, who are the results of their experiments, sometimes wrung from the collective nightmares and phobias of the inhabitants of the city (<c>Dread Slag</c>). And finally, the Golgari have command over Horrors wrought from plant matter and mutated insects that are able to spread on their own by infecting their surroundings with their essence (<c>Woodwraith Corrupter</c>). Sometimes horrors are hunted by the centaurs of the Selesnya Conclave (<c>Hunted Horror</c>).

Shadowmoor

 * In Shadowmoor, the shadow phase of Lorwyn, the races that have survived the change have been thoroughly altered by the tainted darkness covering the plane. Some like <c>Canker Abomination</c> are still recognizable, but others like <c>Grief Tyrant</c> aren't.
 * The lieges from Eventide have enemy-color costs and the Horror creature type <c>Deathbringer Liege</c>, <c>Mindwrack Liege</c>, <c>Murkfiend Liege</c>, and <c>Balefire Liege</c>, <c>Creakwood Liege</c>.

Zendikar

 * On Zendikar, only the <c>Thought Gorger</c> qualifies as a horror, but it could be argued that the Eldrazi are horrors to the extreme.

Notable Horrors
Dominaria
 * Abomination of Llanowar
 * Burke, was a nightmare-horror created by Chainer with the Mirari for Ambassador Laquatus.
 * Greel, a humanoid horror who served the Keldons.

Ikoria
 * Obosh, a Hellion horror.

Innistrad
 * Bruna, after Emrakul's corruption.
 * Kraum, Ludevic's masterpiece.
 * Gisela, after Emrakul's corruption.
 * Brisela
 * The Gitrog monster, a monstrous frog.

New Phyrexia
 * Atraxa, a compleated Angel.

Phyrexia
 * Kerrick, a Phyrexian Sleeper agent.
 * Morinfen and Gallowbraid, two Phyrexian horrors tasked with the destruction of Crovax.
 * Tsabo Tavoc, Phyrexian general during the Phyrexian Invasion of Dominaria.

Zendikar
 * Grakmaw, Hydra Horror.
 * Yarok, an elemental of the wastes of Bala Ged.

Horror manlands and artifacts
Horrors are also created by:
 * <c>Woodwraith Corrupter</c> (4/4 black and green Elemental Horror).
 * <c>Phyrexian Totem</c> (5/5 black artifact Horror with Trample).
 * <c>Dimir Keyrune</c> (2/2 blue and black Horror artifact creature).

Creature Type Update
In (and before) the Grand Creature Type Update the following creature types were changed into Horror
 * Abomination (<c>Abomination</c>)
 * Eater (<c>Eater of the Dead</c>)
 * Fiend (<c>Moor Fiend</c>, <c>Timmerian Fiends</c>)
 * Gatekeeper (<c>Abyssal Gatekeeper</c>)
 * Hell's-Caretaker (<c>Hell's Caretaker</c>)
 * Mindsucker (<c>Urborg Mindsucker</c>)
 * Undead (<c>Hidden Horror</c>)
 * Evil-Eye (<c>Evil Eye of Orms-by-Gore</c>) became a Horror but was later reverted to Eye

Trivia

 * <c>Horror of Horrors</c> is not an Horror but an Enchantment.