Kill Enemies to Open

"Defeat enemies to unlock doors."

— Metroid Prime (British English version)

A trope often seen in Video Games, these doors, treasure chests, barriers, and all sorts of locks won't open until someone kills the enemies surrounding them, as though the seal's integrity were somehow linked to the enemies' lives.

Usually the character has to kill every single enemy in the room/level in order to defuse the lock, but sometimes it might require just a percentage of them, or the elimination of a specific type of enemy like an Elite Mook of some sort.

This trope is often paired with the Ghost Butler in order to force the player to engage with the enemies to escape. Teleporting Keycard Squads also have a tendency to invoke it when they appear, in order to force the player to fight them. Also quite common in Boss Battles, as way to prevent the players from escaping or "unfairly" exploiting the environment to their advantage. Beat 'em Up games often raise Invisible Walls that can only be bypassed this way. May induce Fake Longevity if abused or poorly implemented, as in games that hide enemies to force the player to backtrack.

This is sometimes justified: enemies might harass you when you attempt to open the lock; they might be a Strength Equals Worthiness test, so if you're strong enough to beat them, you're worthy to proceed; they might have keys you need to open the lock; or they might be actively maintaining the lock and defeating them disables it.

Compare and contrast the Gate Guardian, an enemy who personally prevents you from progressing, although these tropes can overlap.

Unrelated to Beef Gate, where the only thing stopping you from proceeding is the threat of imminent death on the other side. Compare and contrast No Ontological Inertia and Load-Bearing Boss, where defeating the enemy brings down much more than just a lock.

A Sub-Trope to Cruelty Is the Only Option and Plot Lock. Related to Plot-Sensitive Latch and Gotta Kill Them All. Super-Trope to Inescapable Ambush.

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Examples:

Action Adventure

• In ANNO: Mutationem, a barrier pops up whenever a room full of enemies is encountered and it remains until all of them have been taken out.
• Castlevania: Curse of Darkness has a few doors that will only open if you've defeated all enemies in the room. Unfortunately, one of these is in a room where the only enemies are Blood Skeletons which resurrect a few seconds after being defeated. How do you defeat them? Bring one of your Innocent Devils who has the ability to permanently kill Blood Skeletons. For your trouble, you get an item that increases your Max HP.
• In Chantelise, barriers prevent you from moving onto the next level unless you have cleared it at least once.
• Eastward: John and Sam do battle with multiple enemies once a room they enter gets locked and is suddenly filled with enemies.
• Most of the games in The Legend of Zelda saga make use of this. Usually, the locks activate after you find an important treasure, or just before you get said treasure. Breath of the Wild has a variant with certain monster camps which contain a treasure chest that can only be opened when all of the monsters have been defeated.
• The Metroid series uses these a lot, usually in the multiple pirate bases you'll have to raid.
• In Owlboy, wiping out all the enemies in some particular areas will make a treasure box appear.
• Star Fox:
  • Star Fox Adventures has its own share of Life Force Doors. They look like red vortexes with a skull in the middle and little "spirits" orbiting around it. That last detail actually has a purpose, as the number of "spirits" indicates how many enemies you need to kill to open it.
  • Star Fox: Assault: As Fox goes on foot across the interior of the Aparoids' homeworld in the penultimate mission, he'll reach corridors and areas where the entrance and exit are blocked by life-force barriers, trapping him so the incoming Aparoid machines attempt to kill him. The barriers will only dispel once Fox dispatches them all.
• Red doors in Ittle Dew must be opened by killing enemies, unlike green doors which use puzzles.
• Luigi's Mansion:
  • Luigi's Mansion: Nearly every first-visited room requires Luigi to suck up all the ghosts in it (not counting hidden Boos) in order to either get the key that opens the door to the next room or get rid of the supernatural vine barrier that protects said door.
  • Luigi's Mansion: Dark Moon: Instead of vine barriers, the game uses purple-colored energy jails that lock up all exit doors until all ghosts in the current area are capture. There's also a special case during the third mission of the fourth area (Secret Mine), when three powered-up ghosts seal the entrance to a cableway car with magical energy chains. These chains are linked to the life force of the ghosts, so Luigi has to hunt them down as he revisits previous rooms.
  • Luigi's Mansion 3 does this rarely, preferring instead to employ scripted ambushes where Luigi has to capture all ghosts in order to dispel the life-force barriers that prevent him from leaving the current room.
• Shantae:
  • Shantae: Risky's Revenge: The second of the Interchangeable Anti Matter Keys in Squid Baron's location, requires Shantae to defeat all the enemies in the previous room from the key's chest's room to unlock the doorway she came from when she was going to get the key.
  • Shantae and the Seven Sirens: Dungeons have rooms that lock on entry and unlock on defeat of all enemies, before important items like Interchangeable Anti Matter Keys.

Action RPG

• Black★Rock Shooter uses two flavors of this with varying requirements:
  • Parts of the stages will sometimes be blocked by a red sigil named Territory Seal, requiring you to defeat the armaments with a red kill mark before proceeding.
  • There are also Territory Box barricades that require you to destroy every armament in the area.
• Diablo III: Several random events involve "cursed chests", which glow with a red light and trigger an attack of enemies when you click on them, who must be defeated to open the chest.
• Fortune Summoners: When passing through a level the first time, the way out cannot be used if monsters are near you.
• Rengoku: Some doors in the second game are marked with an orange flower, meaning they can't open upon entering without defeating the enemies.
• SoulBlazer has this as a core gameplay element. Stepping on a Mook Maker after killing all of its monsters will usually clear away some nearby obstacle or release some sort of NPC.

Beat Em Up

• In Altered Beast (2005), some parts of the levels are locked unless you beat the specific enemies called aptly "Gate Keepers". They're just variants of the common mooks, but with a Battle Aura and more resilience; they also don't respawn unlike regular mooks.
• Fire Emblem Warriors: You'll occasionally come across large gates that are closed and prevent you from going through. To open them, you need to find and kill a specific Captain, usually a Gatekeeper. Barring those, Fort Captains will do.
• In River City Girls, the screen covered in locks when multiple enemies home in, keeping progression halted until there's none of them left.
• Spyborgs: Stage exits are often sealed by Red Barriers generated by the enemy. Every single onscreen mook needs to be killed to deactivate the barriers, allowing access to the next area.

Eastern RPG

• In the Paper Mario games; The Thousand Year Door and Super Paper Mario have the "Pit of 100 Trials", where Mario and his companions face off 100 rooms with enemies (either in an RPG turn-based battle of the former or a Platform Game kill enemy battle for the latter). In TTYD, you must beat all the enemies to make a pipe to the next lower level appear. In Super, you just have to find and kill the mook that's carrying the key that unlocks the door to the next room. You only have five minutes to find the key and open the door, otherwise you get an instant Game Over.
• Science Girls!: The starting area is the 5th floor of the school, and lower floors are unavailable until all the 5th floor rooms are explored, meaning, all the enemies inside them have been killed.

Fighting Game

• Super Smash Bros. Melee: The first level of Adventure Mode features a fighting spot where the player has to dispatch all Yoshis before being able to move forward. And in the third level, should the player reach one of the many fake Triforce chambers, they won't be leave without defeating a Link clone first (though if all of them are defeated before touching the Triforce in the real chamber, the player will be rewarded with a bonus).
• Super Smash Bros. Brawl: Several parts in the levels of the Subspace Emissary require the player to defeat all mooks appearing in one screen so the game allows them to move forward.

First Person Shooter

• Alien Controllers in Black Mesa will occasionally hold doors shut with their telekinetic powers in the chapter "Interloper", thus requiring you to kill them to progress.
• Certain areas in Cabela's Dangerous Hunts 2013 close until you have killed enough animals.
• Every single stage in Deadhunt, where you can't move on to the next level until every zombie, skeleton, knight, giant spiders, or what-have-you are dead.
• Doom:
  • The original Doom:
    • The only way to reach the end of the "Phobos Anomaly" is to kill the two Barons of Hell that serve as the bosses of the level. Doing this will open the way to the outside where the exit is.
    • "Against Thee Wickedly" (E4M6) has a particular nasty example where a Cyberdemon shows up near the barred off exit. The only way to raise said bars is to actually kill the Cyberdemon, and the space you have to fight him is generally very small, so good luck.
  • Doom II:
    • The level "Dead Simple" starts the player inside a cloister with four mancubi, each one on a raised platform. Once all four mancubi fall, the outer walls lower to reveal a fleet of arachnotrons in the outer perimeter. Every spider must also be killed in order to make the platform that leads to the exit rise.
    • The 15th stage of the Master Levels requires defeating groups of enemies to activate contraptions that allow the player to progress, such as the Revenants outside the building to access a teleporter, Arachnotrons to open the inner corners of the buildings, and the last wave of Hell Knights to lower the column holding the blue key.
  • Doom (2016) has a lot of areas under lockdown due to the demonic presence, and that need to be cleared of demons in order to advance.
• Quake II:
  • In both the retail and demo versions, the red card behind the deadly lasers in "Comm Center" won't be accessible unless you kill the Gunner that guards it; the Gunner's death disabling the lasers themselves.
  • In the level "Grid Control", the two Tanks surrounding the entrance to the security grid must be killed before the walls explode... revealing a Super Tank (and a pair of Berserkers in the higher levels).
  • In the level "Big Gun", you need to destroy the Hornet guarding the Laser Guard in the early stages of the level before being able to disable the gun.
• Scathe has a few levels where, instead of finding an exit, requires you to kill everything in an area for an exit to appear. Usually you'll slaughter north of 50 demons, with a handy counter on top of the screen ("38 Demons Remain"...) displaying your progress.
• In Serious Sam video games, there are many areas which close upon entering with doors only opening once the enemies are killed. In the First and the Second Encounter, NETRICSA sometimes tells Sam to kill enemies after analyzing the shut door during combat.
• ULTRAKILL zig-zags this trope constantly, with some encounters completely abiding by this rule, and other encounters allowing the player to completely ignore every enemy and still proceed. Some do both, by locking the main doors but offering side passages out. And others still pull some evil tricks using the Idols (which turn an enemy into an Invincible Boogeyman until destroyed) by locking them away behind barriers that will hold until you kill everything else. The Act 2 Alternate Reality Game explains the existence of the game's enemy encounters: They're all bloody gladiator games for Hell's sadistic entertainment.
• Vermintide II:
  • Several levels include an enclosed area that starts to flood with enemies when you enter past the Point of No Return; once you've killed them all, an exit spontaneously opens.
  • Chaos Wastes expeditions include Chests of Trials that spawn waves of enemies if activated and grant a divine boon when they've all been defeated. Similarly, the final stage of every expedition is an arena level that only grants access to the MacGuffin when you've killed every enemy. Both are framed as tests of worth from the Gods.

Hack And Slash

• Whenever a battle starts in the God of War games, every possible escape route is covered with a wall of flames. The flames vanish after all enemies are slain.
• Doors in the Devil May Cry series sometimes become locked with magical barriers, requiring you to kill all the demons in the room before proceeding. In the first, second, and third games, the demonic barriers will smack you if you try to get close to them.
• In the No More Heroes series, each stage requires Travis taking down various Mooks before he can enter the next area.
• Bayonetta and Bayonetta 2 both use orange-colored barriers that obstruct the progress whenever the eponymous protagonist is ambushed by a group of angels or demons. Interestingly, when all enemies are dispatched, an animation displays Bayonetta breaking the barriers with a blown kiss.
• In Samurai Warriors 2, upon entering the gardens of Odawara Castle's eastern front, the doors will lock all over the place and the player will be ambushed by Fuma ninjas, with no way to get into the castle's main keep. The only way to open them back is to defeat 200 of them.

MMORPG

• EverQuest had a variation on this. The insanely powerful but mostly insane prismatic dragon known as Kerafyrm was put to sleep by Veeshan, the God of Dragons for his crimes against dragonkind. The catch was that four dragons had to spend the rest of eternity as warders to ensure that the spell keeping him asleep was never broken. Players had to kill all four warders in order to wake him up... but the first few guilds in the game to do so quickly found out that waking him up was a bad thing. Kerafyrm would rampage out of the tomb, go over to the city of Skyshrine and go on a rampage there, and then go on a rampage in the Temple of Veeshan before finally leaving for good. This happened once and ONLY once per server. The Warders, who contained exceptionally powerful loot, were dead for good.
• Justified in EVE Online as enemy ships carrying jammers for the acceleration gates which separate mission pockets. Kill the enemy ships and the jamming stops so you can proceed.
• Elsword: This is pretty much inherent in the game system: You can't get to the next area in any dungeon unless you killed all the mobs in the current area first.
• In World of Warcraft, The Burning Legion is very fond of soul-powered portals. To use them, you either need to kill something with a powerful enough soul (multiple not quite as powerful souls work too) in the vicinity of the portal, or bring souls with you for it to burn through. Most player characters and friendly NPCs opt to Pay Evil unto Evil and kill demons in the portal's presence, subjecting the demons to a very well deserved case of Hoist by Their Own Petard.
• All boss segments of Final Fantasy XIV seal off the back exit until the boss is beaten, and the front entrance shortly after the boss is aggro'ed, the latter so people can't circumvent the Weakness penalty upon being Raised/Resurrected, or the need to be raised altogether, by respawning and running back down the dungeon hallway into the fight. There are also frequently spots along the hallways that block progress until some nearby mob/s is/are killed. This is usually a blatant device to prevent players from pulling all the tedious trash mobs between bosses at once and Ao Eing them to death, getting the tedious hallway cleared in a timely fashion.
• Realm of the Mad God:
  • The portal leading to Esben's Inner Sanctum is only opened when all Big Yetis and Snow Bat Mamas in the Ice Cave have been killed.
  • The wall separating the rooms of the Marble Defender and the Marble Colossus will vanish only when the Marble Defender is killed.
  • Killing the Agonized Titan opens the portal to the Cultist Hideout where Malus, his colleagues and their followers hide.
  • Several enemies Item Drop Mechanics have them drop portals to restricted areas when killed: the Stone Guardians drop the portal to Oryx's chamber, while Janus the Doorwarden drops the portal to Oryx's court.
  • Janus himself resides in a locked room that only opens when all the Living Statues in the Castle are destroyed.

Party Game

• Mario Party 7: The minigame Spider Stomp operates this way. Two pairs of characters venture through a jungle where Scuttlebugs have proliferated and then kidnapped a young Flutter. To advance through each segment, the characters have to shoot at the incoming mooks; when no Scuttlebug remains in the current segment, the spider web that blocks the path forward falls down, allowing the characters to advance to the next part. In the final segment, they have to face their queen, who is much bigger and has a lot more HP (it takes 40 hits to defeat her). The first team to defeat the queen and reach the end will rescue the Flutter and win the minigame.
• Mario Party 8: The minigame Boo-ting Gallery has two pairs of characters approach a large mansion during a cloudy night, and from the front yard they have to shoot at all the Pink Boos that appear and disappear at random. Afterwards, the characters enter the foyer and have to dispatch all the Pink Boos located there, and then fall onto the basement to defeat a large Pink Boo whose size reduces with each projectile received until it's defeated. Whoever manages to kill all Pink Boos (including the large Boo at the end) first wins.

Platform Game

• Crash Bandicoot 2: Cortex Strikes Back: In the daytime forest levels, there are trenches onto which Crash has to fall since his jump isn't wide or tall enough to leap past them. Once he's trapped in one, some small mooks begin appraching him. Defeating them all will reveal a bouncy mushroom Crash can use to exit the trench.
• In Rayman Origins in order to rescue the Electoons, you need to dissipate bubbles of dark energy surrounding them by killing the enemies connected to it, (as it seems their life-force is the thing powering the barrier via streams of darkness) before smashing their steel cages to bits.
• In Sonic Rush, some acts will trap the player in a certain area where several enemies appear. The player must then defeat all enemies to escape and continue through the level, with a counter showing how many of them are left.
• Spyro the Dragon:
  • Spyro the Dragon (1998): In the second and third games, on each level you need to defeat a certain number of enemies before special pedestals with powerups become active.
  • The Legend of Spyro: At various points throughout the games, Spyro enters areas where the way forward — and often the way backward as well — becomes shut off by heavy stone doors descending or an Elite Mook summons an Elemental Barrier, which will only be lifted by killing several waves of foes. In some cases this is justified, as with the Dragon Temple being said to automatically seal itself in response to being invaded and only unseal when all intruders are removed, or when the obstacle is a magical barrier created by an enemy who needs to be defeated to dispel it. In other cases, no explanation is provided.
• Super Kiwi 64: One of the Plot Coupon crystals in the Wild West level of the Doomsday campaign is guarded by a group of mechanical sheriffs that roam the haystack yards. Defeating them all is necessary to reclaim the crystal.
• A few instances in the Super Mario Galaxy games require Mario to beat all Mooks nearby in order to make a warp pipe or launch star appear. In the second game, this is the driving concept of Battle Belt Galaxy.
• Donkey Kong 64. Sometimes you have to beat every enemy inside a certain room in order to have golden bananas, switches or bonus barrels show up. A few times, doors are unlocked as well.
• Conker's Bad Fur Day:
  • The game has three examples: A wooden door in the Windy area that opens when the eponymous character kills the big beetles guarding the access to the Poo area (though the door leads to the Barn Boys chapter instead, the Poo zone is open otherwise); a door that leads to the whereabouts of Count Batula's mansion, and opens when enough zombies in the graveyard are killed (the respawn indefinitely, so Conker has to proceed forward when the path is unlocked); the last is a door in the War chapter that opens when a large group of Tediz is dispatched with a gun turret.
  • There's a play with the trope in the last chapter: As Conker and Berri storm the Panther King's castle through the bank, there are security lasers that are dispatched every time a wave of guards is killed, but it's either because Berri manages to disable a particular laser barrier during the spare time between an enemy wave's termination and the arrival of the next, or because Berri kicks a guard towards a laser barrier during a cutscene (in this game, security lasers explode upon contact, as seen previously in the War chapter). After four full barriers are disabled, Conker and Berri reach the elevator and move on to the final part of the game.
• The Treasure Hunter Man series:
  • Treasure Hunter Man 1: The first section of the Sun Tomb is exited by a door that requires killing the yellow enemy at the end to open.
  • Treasure Hunter Man 2: The room in the cave at the far bottom right of the "Windmill at the End" has a door at its top that needs the death of all the monsters inside to unlock it.
• Kirby Star Allies: Some stages have chokepoints in the form of a Multi-Mook Melee, with respawning mooks and sometimes minibosses, which Kirby and co. have to defeat before they can progress.
• Ninjish Guy In Low Res World: In some screens, the exit only opens when all the enemies have been killed.
• Ori and the Blind Forest has a handful of doors that requires killing nearby enemies to open (unlike most doors in the game, which tend to require tricking enemies into breaking them open for you).

Real Time Strategy

• Dawn of War II: Retribution: When trapped on Typhon in the Deranged Chaos Champion's arena, the barriers around the arena will only fall once you kill the Champion, and he only emerges after you kill a sufficient number of orks, chaos forces and tyranids that continuously pour into the arena.
• Dungeon Keeper 2: The final level's Portal Door out of the underworld can only be opened by collecting Portal Gem Mineral MacGuffins from throughout the game and then destroying the two Stone Knight Gate Guardians that bar passage by the forces of Evil. They're Nigh-Invulnerable, but by that point, you have enough villain cred to summon a Horned Reaper that pounds them to dust in a Cutscene.

Roguelike

• The Binding of Isaac: Taking its cue from the dungeons in The Legend of Zelda, entering any room containing enemies results in every door locking (including the one you came in through) until you kill them all. Challenge rooms, which are initially empty, have the doors seal if you accept the challenge and spawn the enemies in. However, the game also features a twist to it, as it's possible to force your way out of a room containing enemies by blasting the door with a bomb. (Either yours or fired by an enemy). Of course, this tactic must be used sparingly because bombs are a precious commodity most of time, and doing so doesn't take care of the enemies inside the room, so if you walk back into it, you'll either have to deal with the enemies, or use another bomb to escape once again. Also, this tactic doesn't work in boss' (nor mini-boss') battles, because their doors are blast-proof... Just like every single door in the game's Brutal Bonus Level.
• Other action-roguelikes have, in turn, copied this approach, minus the bomb part. Enter the Gungeon and Hades both frequently make you clear out multiple waves of enemies, and the latter also bars you from going back to previous rooms.
• In the first Risk of Rain, after surviving long enough to charge the Teleporter, you need to kill all remaining enemies in order to proceed to the next stage.

Third Person Shooter

• Jet Force Gemini features obstacles called Life Force Doors which can only be opened by killing enemies.
• Splatoon: In many single-player levels in the series, there are parts where it's necessary to dispatch all enemies present in order to enable the launchpads that take the player's Inkling to the then-following areas.
• Vanquish: Prevalent in a sense that almost every scripted sequence and cutscene will only trigger once all enemies in the current area are defeated.

Western RPG

• A staple in the Mass Effect series, where you usually required to clear out each room before you are allowed to proceed.
• Fable
  • In Fable:
    • The Hook Coast connection in the Cullis Gate Portal Network is a Broken Bridge that requires the Hero to destroy a wave of undead near the Darkwood's Ancient Cullis Gate, reactivating the Gate with their Life Energy.
    • One of the Demon Doors believes that Strength Equals Worthiness and only opens for a Hero who can defeat all the waves of progressively stronger Hobbes that it summons.
    • At the beginning of the "White Balverine" quest, Knothole Glade is locked down and won't open its gates until the Hero defeats the waves of Balverines in the forest outside. Justified since the gates are there for that specific purpose.
  • In Fable II, several doors in the Storm Shrine only unlock and open themselves when the monster in the room is killed — especially strange, as some of the monsters are said to have moved in after the Shrine fell into disuse.
• Near the end of the main quest in The Elder Scrolls III: Morrowind's Tribunal expansion, you'll need to defeat the "Imperfect", a humongous Fabricant who guards the final room in the Clockwork City. You won't be able to open the door to the final room until the Imperfect has been slain. Notably, this trope is often averted elsewhere in the game, as it is perfectly reasonable to sneak past enemies and pick locked doors. (The game has very few Plot Locks.)
• Vampire: The Masquerade - Bloodlines: When the Mandarin kidnaps the fledgling vampire Player Character to test how Our Vampires Are Different, one hapless Mook is Trapped in Containment with the vampire and a wholly ineffective crucifix. Unfortunately for the Mook, killing him is the only way to open the chamber door and advance the quest.

Wide Open Sandbox

• Terraria:
  • During Slime Rain, killing 150 slimes summons King Slime. If you've done it once before, only 75 are needed.
  • During the Lunar Events, in order to damage a Celestial Tower, one must first kill 100 enemies (150 in Expert Mode) from within its section, which removes the shield that protects the Tower and makes it vulnerable to attacks.

Shoot 'em Ups

• Bangai-O Spirits uses special blocks that have an arrow icon pointing at a specific direction of the level. These blocks will only break when all enemies and targets located within the range and width of that direction are eliminated. For example, a block whose arrow points to the left will be protected by the life force of the enemies located at the left, upper left and upper down areas of the level. A block whose arrow points to the bottom right will break when the player destroys the enemies found at the bottom, right and bottom-right areas. This can be used cleverly in custom levels to make some ingenious mazes.
• Hyper Princess Pitch: Your goal is to Shoot Everything That Moves in Mecha Santa's factory, one room at a time. The doors to other rooms only open after all the enemies in a room are destroyed.

Other

• Rock Solid Arcade's Web Games Robokill and Robokill 2. When you enter a new room there are no exits. You must kill every opponent in the room before the exit(s) will open.

Non-Video Game Examples:

Film - Live Action

• In Mighty Morphin Power Rangers: The Movie, the rangers encounter a large stone door that blocks them from reaching the "great power" stashed in the monolith on the planet Phaedon. On the door are four life-sized carvings of warriors that come to life to fight the rangers. It's only after the stone warriors have been dissolved, disintegrated, or crushed in combat that the door finally opens.

Tabletop Games

• Mice and Mystics: Players can only Explore to enter a new map tile after all enemies on their current map tile have been defeated, no matter whether the exploration involves opening a barrier, escaping Down the Drain, or just walking farther down a tunnel.

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