Alice is a Sealed Evil in a Can. Bob, either because he was promised something like immortality or riches, thinks he can control her, or because he thinks Alice isn't as evil as everyone says she is, tries to free her. After a bit of hard work, and possibly some outmaneuvering of people with more common sense, Bob frees Alice. However, rather than rewarding Bob for his service or even giving him a simple thank you, Alice tosses Bob into her mouth and eats him without a second thought.
This trope when somebody frees or summons a Sealed Evil in a Can, and is immediately eaten or otherwise destroyed by said evil. Often a trope that appears at the climax of a story. A sub-trope of Evil Is Not a Toy and a common fate of cultists summoning an Eldritch Abomination. One of the hazards of calling up what you can't put down. It's also a sub-trope of You Have Outlived Your Usefulness.
- This happens to Samantha the necromancer in episode 3 of Soul Eater when she summons Wrath of the Pharaoh, because of all his undead subjects, of whom she'd taken control by that point.
- Jaune Arc, Lord of Hunger: In the chapter "Legends", a group of Sith cultists attempt to acquire the Mask of Darth Nihilus in order to reawaken the ancient Sith Lord's spirit. Upon being awoken, one of the first things that Nihilus does is turn on the cultists who summoned him and drain them of all their Life Energy. Justified since Nihilus's soul needs to feed on the Force to survive and had been spending thousands of years trapped in complete isolation within his mask. By the time he woke up, he was starving and instinctively attacked all living things within his vicinity.
- In The Bartimaeus Trilogy, it's generally stated that demons will attempt to eat their summoners if they fail to draw a proper pentagram or stray outside it. Bartimaeus himself alludes to having eaten a few wizards who made silly mistakes in the past. In book two, a wizard is eaten by a demon because he copied the summoning circle from a book whose printer had deliberately drawn it wrong in revenge for the wizard assaulting and crippling his son years earlier in the prologue.
- In The Belgariad and Malloreon by David Eddings, this is a common fate of Demon-summoning sorcerers. The sorcerer can only maintain control of a summoned demon by continuously forcing it into a shape he controls, correcting deviations with more magic. If he gets it wrong, he gets eaten, generally followed shortly by everyone else in the vicinity.
- In The Last Battle, Shift uses the humans' fear of Tash to increase his own wealth and fame. This involves posing as Tash's high priest/chosen one and constantly threatening to sic Tash on Shift's enemies. The real Tash eventually learns about this, and he is not impressed.
Tash: Here I am. What hast thou to say?
- The advice given in The Case of Charles Dexter Ward
I say to you againe, doe not call up Any that you cannot put downe; by the Which I mean, Any that can in Turne call up somewhat against you, whereby your Powerfullest Devices may not be of use. Ask of the Lesser, lest the Greater shall not wish to answer, and shall commande more than you.
- In Samurai Sentai Shinkenger/Power Rangers Samurai, Dayu's reward for fully restoring her master is to be immediately absorbed so he gains a human side and thus immunity from the sealing spell that kept him in his can for most of the series.
- In the episode "Die Hand Die Verletzt" of The X-Files, Mulder and Scully investigate a seemingly Satanic-inspired murder in a small town. Turns out the killer is none other than Satan himself, who was summoned by the locals through rituals to advance their careers, and he's pissed because they aren't true believers.
- In Pathfinder, Daemons stand out among Evil-aligned Outsiders as Omnicidal Maniacs that will immediately try to devour their summoners, body and soul, and usually continue to try even if they get roped into a Magically Binding Contract. While Devils will try to ruin their summoners with bargains and Demons encourage For the Evulz-style debasement, Daemons just want all life to end.
- Magic: The Gathering invokes this trope via Feaster of Fools, a Demon that has both Convoke (meaning that your other creatures can help you summon Feaster of Fools) and Devour (meaning Feaster of Fools can eat your other creatures when summoned to get stronger, which most likely will be the same people that Convoked it).
DCI Ruling: "[Feaster of Fools] can devour creatures that convoked it, and those creatures can reflect upon the wisdom of convoking a demon."
- In Dark Cloud, once the Dark Genie is free, it eats the person who organized the ceremony. The creature justifies this by saying that it hadn't eaten in 400 years and was hungry.
- In the finale of Mega Man Battle Network 3: White and Blue, Lord Wily's consciousness (he pulled a Brain Uploading earlier) is consumed by the Psycho Prototype Internet that he awakened and unleashed on NetSociety, Alpha.
- A notorious and memetic example occurs in World of Warcraft with gnome warlock Wilfred Fizzlebang, self-proclaimed Master Summoner, whose botched attempt to summon a doomguard ends up with him unleashing something much more powerful and hammier - the Eredar Lord Jaraxxus. It doesn't end well.
Jaraxxus: TRIFLING GNOME! YOUR ARROGANCE WILL BE YOUR UNDOING!
- On that note, for a while it was possible for a player character warlock to meet this fate when summoning Doomguards and Infernals, as instead of being bound fully to the warlock like their regular pet demons, these two were by default hostile and only controllable via the notoriously unreliable Enslave Demon spell, which had a tendency to break at the worst possible moment, making these demons Awesome, but Impractical for purposes other than griefing in low-level areas. Later expansions made them less impractical.
- Occurs in the in-game book A Tragedy In Black in The Elder Scrolls V: Skyrim, wherein a child uses a spell to summon a Dremora to help him enchant a dress for his mother's birthday. The Dremora offers him a Black Soul Gem (in the Elder Scrolls universe, enchanting is done by trapping and using the souls of other creatures), which the boy accepts. It turns out that accepting a gift from a conjured creature breaks the binding spell that forces it to obey the summoner's will. Fate Worse Than Death of a Child ensues.
- Girl Genius: The monster the Quintillius Harmon and his cultist minions summon makes an attempt to eat him before he ascends and gains control over it.
- A staple of The Unspeakable Vault (of Doom) is Cthulhoo eating cultists that just summoned him.
Cthulhoo: Yum yum!