Some Artifacts of Doom are dangerous because they are evilly sentient and want to subvert you to their ends. Others are dangerous because they are keys to open a portal to some place of big bad nastiness, whether it be Hell or whatever place Eldritch Abominations come from, or because they have the power to summon the big bad nastiness into this world. This trope is about these kinds of artifacts.
Many Tomes of Eldritch Lore are also artifacts of this kind, unleashing any number of nasty things upon the world when some poor Genre Blind fool makes the mistake of reading the book in question aloud. Other artifacts might require some other means of activation, especially if they're being used as the linchpin of some Big Bad's Evil Plan.
- The Behelits from Berserk, which act as a key to the Astral Realm where the Godhand live, and are activated when their bearers cross the Despair Event Horizon. Normal Behelits are used by humans to become Apostles, while the Crimson Behelit, which appears once every 216 years, is used by its bearer to become a new member of the Godhand during the Great Eclipse, and in both cases, a sacrifice is required.
- The Demon Summoning Pot from Senyuu., which Ruki accidentally uses to summon a host of demons when she mistakes it for a popcorn pot.
- The Necronomicon Ex Mortis (not to be confused with the Necronomicon associated with the Cthulhu Mythos), which was accidentally used by Ash from the Evil Dead series to summon some big bad nastiness from Hell which proceeds to mess up his life in ugly fashion.
- The apartment building in Ghostbusters (1984), which acted as a gateway to the realm of Gozer the Gozerian.
- The Lament Configuration in Hellraiser, which summoned the Cenobites, sadomasochistic demons that took the summoner(s) back to hell and tortured them. The boxes are actually a more reliable way to summon the Cenobites, as they were commissioned in the 18th century by a bunch of devil-worshippers who had to go through a pretty elaborate ritual at first.
- The Cabin in the Woods has a basement full of evil summoning artifacts, including shout-outs to some of the most famous ones. The only question is which one the college kids will activate.
- The Lemarchand's Boxes from Clive Barker's horror stories, the most famous one being the Lament Configuration from The Hellbound Heart, the novella that would be adapted by Barker himself into the original Hellraiser, which acts as a key to the realm of the Cenobites when somebody solves it.
- William Hope Hodgson's Carnacki the Ghost-Finder stories. In "Gateway of the Monster", the title being (a giant strangling hand) enters our world through the Luck Ring of the Andersons - a small pentagonal ring. It was originally activated by being worn, but continued to summon the monster afterward.
- The Shining Trapezohedron in H. P. Lovecraft's "The Haunter of the Dark" summons the titular Haunter, an avatar of Nyarlathotep (it also gives you visions on the Outer Void and of its own history, but summoning an Eldritch Abomination is clearly its main function).
- Robert Asprin's Thieves' World, Poul Anderson's short story "The Gate of the Flying Knives". The title gate is a large parchment 8 feet long and 4 feet wide. Through it, sikkintairs (dragon-like monsters controlled by the Ilsig gods) can be summoned to carry off or kill people.
- Michael Moorcock's Swords Trilogy. Corum Jhaelen Irsei has a hand cut off and one eye put out. He is given two artifacts to replace his lost body parts, the Hand of Kwll and the Eye of Rhynn. With the Eye he can see into an other-dimensional cave, and with the Hand he can beckon the inhabitants of the cave to come to him and fight his enemies. Anyone killed by the summoned creatures replaces them in the cave for the next summoning.
- Thoth-Amon's Ring of Set from the first Conan the Barbarian story, "The Phoenix on the Sword," which the sorcerer used to call down an Eldritch Abomination to destroy his tormentor and everyone with him.
- The Mortal Instruments can be used once every thousand years to summon the Angel Raziel and request a favor from him. In theory the summoner could compel him to grant the request, but this is a very unwise thing to try given that he is a powerful archangel.
- In Fancy Apartments, the Big Bad is summoned using a demon's horn... By accident. And the summoning gets messed up mid-way, so the Big Bad spends most of the story trying to fully materialize.
- De Umbrarum Regni Novem Portis, or Of the Nine Gates of the Kingdom of Shadows from the novel The Club Dumas and its cinematic adaptation The Ninth Gate is said to have the power to summon the Devil himself from Hell and grant his summoner immense supernatural power. It is also said to be an adaptation of a much older Tome of Eldritch Lore called the Delomelanicon, written by the Devil himself.
- In The Bartimaeus Trilogy, a summoning horn is this. It allows a magician to quickly summon a powerful spirit without the tedious time-consuming chanting of incantations. This is amply demonstrated in The Amulet of Samarkand when Simon Lovelace uses one to summon Ramuthra, a monstrous spirit capable of warping reality itself, in seconds instead of hours.
- In Robin Jarvis' The Oaken Throne, the Silver Acorn pendant is stolen by the High Priest of Hobb, who uses it in conjunction with a ritual sacrifice to summon the evil rat god into the world.
- Destroy the Godmodder sometimes has this as player or NPC summons that must be defended for a few turns before functioning. If they manage to survive until their activation, everyone knows to hit the deck, because if whatever it is finishes the summon... Well, these attacks always end poorly for at least one side. One of the most infamous examples is when the Godmodder used the Black Monolith to summon a past version of himself.
- The "Grimoire for Summoning the Zoologically Dubious" from Homestuck.
- The strange program that summons Lord English definitely also counts as one of these.
- The Dragon Balls of the Dragon Ball series can be used to summon the Eternal Dragon, a wish-granting dragon. Depending on the series, it can grant anywhere from one to three wishes with varying restrictions, depending on which dragon is being summoned from which set of Dragon Balls.
- Possibly derived from Lohengrin (see Theatre, below) (as C. S. Lewis was a big Wagner fan (though it may come from Astolfo's horn in Orlando Furioso — or both), Queen Susan's horn in Prince Caspian is blown to summon aid to the army of the Old Narnians.
- In Dragon Bones, magic-bound slave Oreg can be summoned using the ring to which he's bound. The problem is that his magic is limited and he can't teleport away again.
- The Elantrians in Mistborn Secret History have something best described as this, a ball of glowing raw Connection that will let them take up the Shard Preservation when it's holder dies.
- The Wheel of Time has the Horn of Valere, an artifact which summons the great Heroes of the Ages to come and fight for the one who blew the Horn.
- But they aren't necessarily good. They're tied to fight for whoever blows the horn, not for good. So it's sort of borderline... However, the last book reveals that, contrary to what popular in-universe opinion says, the Heroes will fight for any mortal who blows the Horn. They will not, under any circumstances, fight for the Shadow.
- The first and subsequent editions of Dungeons & Dragons had the Horns of Valhalla, that could summon heroes from Asgard to fight for the possessor. Of course, if you didn't meet the requirements of being able to use them, the summoned berserkers would turn on you.
- A Ring of Djinni Calling does just that—it summons a genie to serve its wearer for an hour per day. Based on the story of Aladdin, of course, though unlike the Genie of the Ring in that story, the genie isn't inside the ring, it's actually summoned from another plane of existence.
- In Lohengrin, the eponymous Swan Knight, forced to leave his wife, gives her a horn to give to her brother if she ever sees him again, promising that the horn will bring aid in danger (presumably when blown).
- The summons in the Kingdom Hearts series are obtained by finding an object associated with the character, usually a gemstone or charm of some sort. For example: the Fire and Nature gems summon Mushu and Bambi respectively and the Ukelele charm calls Stitch.
- There are three Summoning Artifacts in Tales of Monkey Island Chapter 2: The Siege of Spinner Cay, all of which can be combined into one Summoning Ball Artifact used to summon the Sea Creatures to help Guybrush find the alleged resting place of La Esponja Grande. And it's no wonder that McGillicutty and his crew want the artifacts so they can stay with being Poxed that way once they destroy the magical voodoo sponge.
- There is a fine and proud tradition to use technology in this capacity in the Shin Megami Tensei franchise. Most examples involve wearable computers in the form of gloves or other such lightweight, portable equipment such as handheld video game consoles or cell phones, though at least in the Devil Summoner continuity, summoning tech has been incorporated by certain individuals into such oddball equipment as guns, brass knuckles, and a saxophone.
- In Fate/stay night, specific Heroic Spirits can be summoned if one has an appropriate catalyst, which consists of something associated with the hero in question, or something from their legend. This includes things like one of their weapons, a piece of their clothing, or a fossil.
- The Hex Gate Disk in Edict Zero Fis is a borderline case; the holder can summon and control creatures using the device. Whether this is good or bad depends on the holder of the artifact.