Thor: I don't. Mother did. You should know that when we fought each other in the past, I did so with a glimmer of hope that my brother was still in there somewhere. That hope no longer exists to protect you. Betray me, and I will kill you.
Loki: [smiling] When do we start?
This trope is about making a deal with or helping the enemy or the opposition in order to further one's own goals. Often, the thought behind this is to give up a short-term advantage or benefit for a more long-term or lasting one. The cooperation need not be mutual or completely honest, as long as the terms of the deal are honoured and no coercion is involved. Some hypothetical examples include:
- Providing information to the opposition on where they can find an important artifact, hoping that this can keep them distracted enough that you can find a more important or useful item.
- Treating your prisoners well, and agreeing on prisoner exchanges, in the hope of your enemies treating their prisoners well as well, and that the enemy forces will surrender instead of fighting to the death.
- Trading one important item for another. Both sides get what they want (or maybe deprive the other side of what they traded for) without the need for a battle (e.g. the heroes want that silly looking stone and the villains are willing to trade it for that rusty old sword).
- Making a temporary truce on the understanding it'll be business as usual afterwards. Working together for a goal they know only one of them can obtain in the end (with the benefits of cooperating outweighing the risks of the other side snatching it first) is a common cause.
This sort of thing is never a Heel–Face Turn/Face–Heel Turn (although it can be part of a Hazy-Feel Turn, especially if a Wild Card's involved) - the character or faction in question is still working towards their original goals. A low level hero or minion might still work against the boss's wishes (e.g. they let a prisoner go because they think they're more effort to keep imprisoned than they could get from holding them hostage... or maybe to keep their leader from Jumping Off the Slippery Slope), however. At its most extreme, a character might join up as The Sixth Ranger (either as a representative of their side or working on their own initiative).
Super-Trope to Enemy Mine (where the "deal" in question is joining forces for the specific purpose of overcoming some sort of threat to both sides), examples of which belong on that page.
The Enigmatic Minion is especially prone to these with the heroes, and someone of any morality might suffer a Neutrality Backlash. If both sides join forces, it might lead to Teeth-Clenched Teamwork. Compare Punch-Clock Villain/Punch-Clock Hero, Go-Karting with Bowser, Deal with the Devil, Villain Team-Up, and Pragmatic Villainy. Contrast Hostage for MacGuffin and "Blackmail" Is Such an Ugly Word (for unfair deals).
- In Pokémon: The Series, Team Rocket have helped Ash and Co a couple of times to further their own plans. For example:
- In "Pokémon Scent-sation!" they helped him sneak into an all-girls gym he'd been banned from by dressing him up as "Ashley" and posing as "her" parents. This allows them to plant a smoke bomb so they could break in later (although they let him assume they were doing him a favour for helping them when they were stuck in a tree).
- On more than one occasion (the first being "Electric Shock Showdown") they cheered him on with the excuse that it'll mean Ash's pokemon will be stronger "when" they steal them (particularly in the Pokemon league episodes).
- In one episode, James acquires May's egg, while May finds his Mime Jr.. When the rockets confront Ash et al, James immediately hops out of Team Rocket's mecha, cheerfully offers to trade with May (which they do), and then hops back in to continue their Evil Plan.
- Jesse and James almost always side with Ash against Cassidy and Butch, either genuinely or to try and seize control of their plan. Apparently their rivalry with the other duo trumps their loyalty to the larger Team Rocket.
- In One Piece, Trafalgar Law, who previously considered himself a rival to the other Supernovas — the Straw Hats in particular, forms an alliance with the Straw Hats to defeat Kaido (one of the Four Emperors) by cutting the weapons supply from his client, Doflamingo. Turns out Law was really after Doflamingo himself. Kaido is merely his backup plan and he used the Straw Hats to destroy Doflamingo's weapons factory so that Kaido will punish him for it.
- This is the entire basis of Kurosagi & Katsuragi's relationship in Kurosagi. Kuro needs information to hunt down swindlers and Katsuragi gives it to him if it's someone he wants taken care of.
- In Someone to Watch Over Me, after both Ladybug and Hawkmoth learn each other's identities, Gabriel outlines his plan to make a Wish with minimal backlash. Neither Ladybug nor the Guardian are keen to work with him, nor to let the Wish be used, but they can tell that he's thought things through, and they don't want all-out war, either. In the end, it would have gone according to Gabriel's plan if he hadn't tried to betray them partway through, and the cost of the Wish leaves him in a coma.
- When Simi and Akash are tied up by the organ harvesters in Andhadhun, she suggests that she untie his hands in exchange for getting her blindfold removed by him afterwards, so she can guide him. He reluctantly agrees as he has no better options available. She proceeds to send him on a wild goose chase so she can find something to cut her own ties with while he's distracted, and then attacks him.
- In Avengers: Age of Ultron, when the Avengers are clearly going to overcome HYDRA's forces, Strucker plans to surrender to the Avengers and hand over the advanced weapons HYDRA has developed, in the hopes that they'll take it at face value and ignore the more dangerous work HYDRA is up to. It doesn't go quite to plan, since the Maximoff twins disobey orders to fight the Avengers, and Tony ends up finding their secret lab anyway.
- The entire plot of Exam. All eight candidates are vying for the same job, but they agree to work together fully knowing only one can advance. Some are more genuine in their cooperation than others.
- The Great Race. After Professor Fate and Maggie DuBois are kidnapped by some bad guys, Fate's minion Max joins forces with the Great Leslie to rescue them. Of course, being a villain, Max betrays the heroes during the rescue.
- In Ocean's Thirteen, the group gets financial sponsorship from the villain of the first two movies in exchange for the profits. The main characters are happy with this deal, since it's not about the money this time.
- The premise of the Wuxia movie Warriors of Heaven and Earth is based around this sort of deal between a military officer named Lt. Lai Qi and his predecessor, Lt. Li (who deserted). It turns out that Li has sworn to escort a group of monks (and refuses to come quietly if he's not allowed to do so), so Lai Qui agrees to help him escort them on the understanding they'll resume their battle afterwards.
- One of the main strategies adopted by Mike Stearns in the 1632 books. The time-displaced Americans, for example, teach everyone they meet (friends, opponents, or enemies) how to make the antibiotic chloramphenicol. They know that any major production will require them to educate their workforce, and thus let in more radical ideas. Stearns also directly advises his political rival Wilhelm Wettin in how to build an effective political party that could rival his own, because Stearns is a true believer in the principles of American democracy whereas Wettin and his allies are honestly new to it.
- In Jules Verne's Around The Worldin Eighty Days, the valet and the police inspector come to an agreement to help each other as long as Fogg is out of British territory — the inspector wants to arrest Fogg for a bank robbery, the valet is trying to help his boss finish his world trip.
"Friends, no, allies, yes, but at the slightest sign of treachery I'll wring your neck."
- In the Ciaphas Cain novel "For the Emperor", Cain's unit is stationed on a planet that's on the verge of civil war thanks to the Tau attempting to annex it. Neither side wants it to break out (yet), leading to a lot of this. Early on, a Kroot mercenary saves Cain from being beaten to death by Tau sympathisers. Much later, Cain helps a Tau ambassador get medical treatment and escorts him back to his compound (even having to order the guardsmen under his command to shoot some loyalists who wanted to lynch the Tau).
- During the course of Solo Command, General Han Solo (of the New Republic) and Admiral Teren Rogriss (of The Empire) come to this sort of agreement concerning their mutual foe Warlord Zsinj. In particular, they covertly hand one another intelligence about Zsinj's covert operations and privately-owned companies, which they put to good use crippling his operations. They also participate in one joint effort to ensnare him; though it's unsuccessful, there's no sign of treachery.
Rogriss: "Once we're done with him, we can go back to our very personal ideological differences, without having to invite anyone else to play."
- Discussed in The Traitor Son Cycle when Harmodius accuses the Wyrm of Erch of this. The dragons don't want to see humans become powerful enough to cause them trouble, yet Ash is an immediate problem, so Harmodius speculates that the Wyrm presents himself as their ally right now only to become their enemy once his omnicidal kin is taken care of.
- Kane and Lages form an unlikely alliance at the end of Darkness Weaves, since they both want to see Efrel dead—even though they have been actively trying to kill each other for a good half of the book. They still do not trust one another and the only thing that unites them is a common enemy. Due to said enemy's cunning, the alliance lasts even shorter than it was supposed to.
- In The Flash (2014), Captain Cold (Leonard Snart) and The Flash force each other into one. Snart has learned the Flash's Secret Identity and will tell (or broadcast it to) the world if Flash captures him or gets him arrested. Flash grudgingly lets him go, but sternly warns him that if he kills anyone or harms any of his friends/family, then all bets are off and he'll put Snart away regardless of him revealing his identity. Snart's subsequent Heel–Face Turn in the spin-off Legends of Tomorrow, which resulted in him being Killed Off for Real rendered this agreement permanent.
- Daredevil (2015): Wilson Fisk spends season 3 running a gambit where he leads Ray Nadeem to think he's cooperating with the FBI as an informant, while actually using the FBI to take down criminals and any other individuals who are threats to his criminal empire.
- In Doctor Who, The Master engages in this numerous times with the Doctor, and also with companion Clara Oswald.
- The Gifted (2017): It's eventually revealed that Season 2 Big Bad Reeva Payge (a mutant supremacist and leader of the Inner Circle) and Benedict Ryan (a human supremacist talk show host) are secretly working together to increase the tensions of human-mutant relations into a full-fledged race war, in order to bring about the outcome they both want — humans and mutants being forced to live apart in separate nations.
- Mass Effect: Andromeda: Towards the end of the game, the Primus engages in one of these, offering Ryder a shot at attacking the Archon in exchange for getting rid of him. She still wants to take over the Heleus Cluster and exalt everyone there, Ryder included, she just objects to the Archon's methods (and increasing megalomania). It's entirely up to the player whether to take the offer or tell her to get lost.
- Occurs late in Modern Warfare 2. Both Task Force 141 and Makarov are betrayed by the true puppetmaster of the war, General Shepherd, so Makarov provides Captain Price with the location of Shepherd's base in order to allow all of his enemies to fight each other.
- In The Order of the Stick, Therkla the half-orc Ninja tries to find a compromise between Hinjo and her master Daimyo Kubota's agendas (albeit because she had a crush on Elan). Kubota kills her so he can use her as a scapegoat.
- In the Noob, Fantöm gets to a point where he has to repeat one of his biggest feats, single-handedly beating an ex-Final Boss meant for a group of at least four players. However, the boss in question got a few updates since he last did it, including a big explosion that happens after the boss gets beaten. He survived that surprise only thanks to Spectre, the top player from another faction, who didn't like the idea of Fantöm's effort being ruined by a last-minute snarl. According to the novel version, the reason Spectre was present in the first place was that he was studying Fantöm from a distance to prepare for a future battle against him.
- This happens several times on DuckTales (1987):
- In "Beaglemania", Scrooge cooperates with Ma Beagle to destroy the Beagle Boys' musical career.
- In "Magica's Shadow War", Scrooge teams up with Magica to stop her magically animated shadow, and ''its'' shadows, from taking over the world.
- In "Robot Robbers" Scrooge and Flintheart Glomgold cooperate to halt Ma Beagle and the Beagle Boys, who'd stolen Glomgold's giant construction robots and were running amok across the city.
- In "Time Teasers", Scrooge cooperates with the Beagles to escape pirates and get back to the future.
- In the Futurama episode "Mother's Day", Mom has set off a Robot War (with a remote control that forces all the robots in the world to rebel) because it's the anniversary of the day she was spurned by Prof. Farnsworth. Her sons try to end the uprising and make her happy by tracking down Farnsworth and getting him to get back together with her.
- Averted by Buzz Lightyear of Star Command; one episode has Zerg deposed by another villain and he spends it watching Buzz et al trying to fight the new threat without offering any help (apparently on principle).
- In the Dexter's Laboratory episode that introduces Dexter's rival Mandark, when Mandark falls in love with Dee Dee and finds out she's Dexter's sister, he begs Dexter to help get them together. At first, Dexter is hesitant to help him, until he realises if Dee Dee gets into Mandark's lab, she will end up accidentally destroying it.
- In the Transformers episode "The Return of Optimus Prime," the last few uninfected Autobots are forced to team up with the last uninfected Decepticon, Galvatron, in order to stop the Hate Plague. At one point, the Autobots' human ally Jessica Morgan asks if Galvatron can be trusted, to which Kup replies, "Not for an instant."