Final Boss, New Dimension

""Going to some other dimension to fight a final battle is such a cliche!""

- Xiaomu, Super Robot Wars OG Saga: Endless Frontier

You're off to fight the Final Boss, so you end up having to go to another dimension. A Video Game trope, probably caused because the developers want it to be memorable, impressive, and/or awesome. May very well have an Amazing Technicolor Battlefield or be a High Altitude Battle. It might also come with a Surreal Theme Tune. The main thing, however, is that it's in its own dimension, universe, or whatever. Fighting the boss in a different time period also counts. May also be applied to Bonus Bosses, even though they're not the final boss. A common part of Trippy Finale Syndromes, it is usually to be found in The Very Definitely Final Dungeon. Depending on the characteristics of the new dimension, it may or may not invoke Interesting Situation Duel. Sister trope to Amazing Technicolor Battlefield. Done wrong, it can lead to Disappointing Last Level.

But in a sense it can mean bringing the fight to them and minimalizing damage to your own world. Maybe the Final Boss can only exist in that dimension and may be just using pawns to spread its influence and envelop the other dimension so it can exist there also.

Anime & Manga

 * In Tengen Toppa Gurren Lagann, the final battle takes place in a pocket universe.
 * In New Getter Robo, the Oni Gods are faced in a universe made of Getter Energy.
 * Beyblade: At the end of the first series, Takao and Yuri (get your minds out of the gutter) are warped into an otherwordly, frozen wasteland during their game. The outside just sees an enormous, spiked block of ice.
 * Apocalymon, the final Big Bad of Digimon Adventure, was fought in a strange void that is neither in the Digital World nor the physical world. Digimon Adventure 02 had its final battle in the Digital World, but the first phase of the battle was fought in yet another plane of existence. Digimon Frontier's final battle took place literally in the void of space, and its climax happened in a wormhole tunneling between the real and digital worlds.
 * The fight for Star Memory in Rave Master takes place inside Star Memory.
 * The fight with the original Demon Lord in Superior takes place in a weird pocket dimension that may or may not be a physical representation of their mind.

Tabletop RPG

 * Judges Guild adventure Dark Tower (1979), using Dungeons and Dragons rules. The final battle against the Big Bad Pnessutt the Lich took place in the highest level of the Outer Plane of Hades. The party had to activate a planar portal to reach him.

Video Games

 * The Bonus Boss Culex in Super Mario RPG: Legend of the Seven Stars is fought inside an alternate dimension that appears to be somewhere in the Final Fantasy universe, probably near the Final Fantasy IV reality/world/whatever, judging by the music.
 * The final dungeon and boss also reside in an alternate dimension: Smithy's home dimension, in fact.
 * Super Robot Wars OG Saga: Endless Frontier has its final battle in the Einst dimension. It also has the final battle between the Namco characters Reiji and Xiaomu and their foe, Saya, which, while not the final boss of the game, counts because the game's dimension is an alternate dimension for them. Ironically, the page quote is for the latter, not the former.
 * And the former is a Call Back to the final battle of its predecessor Super Robot Wars Original Generation 2, which also takes place in the Einst dimension. Of course, the True Final Boss takes place back in normal space.
 * In OG Gaiden, after defeating Dark Brain, you're taken to another dimension to fight the True Final Boss, which is....
 * The final Specter fight in Ape Escape is fought in Dimension X, if the stage name in the NTSC version is to be trusted.
 * Cult classic Legend of Dragoon has one of the most fantastic examples of this throughout all RPGs, as the final battle takes place through the course of an entire world's creation, lifetime, and destruction. You go from Amazing Technicolor Battlefield to the chaotic upheaval of a world being born, to new life flourishing across it. You see the entirety of history come to pass through archaically-styled still images, ending with a prominent image of Death. And the grand finale of the fight takes place atop a ground composed of the corpses of everything that had lived on that world.
 * Super Smash Bros Brawl: The Subspace Emissary has the final boss fight with Tabuu in the realm of Subspace.
 * Any of the Super Smash Bros series, actually - the fight with Master Hand (or Crazy Hand) takes place in some sort of other-dimension (this is, of course, before Subspace Emissary came up).
 * At the end of Half-Life, the game's Silent Protagonist is transported to another dimension (the former Trope Namer for Disappointing Last Level, Xen Syndrome). In this dimension, his mission is to destroy the game's Damage Sponge Boss, the Nihilanth.
 * The Final Fantasy series is fond of this trope.
 * In the "Dawn of Souls" remake of Final Fantasy I, once the party encounters Chaos, they are spontaneously whisked away into a psychadelic warp zone. In both the original and the remake, the entire final dungeon is
 * Final Fantasy V does it by unleashing, and along with it.
 * Final Fantasy VIII's final battle against starts out fairly normal, taking place in her throne room. Over time, the arena becomes more and more chaotic, until the party is whisked away into a dimension devoid of light and substance.
 * Final Fantasy IX has the infamous fight against Necron, which apparently takes place in.
 * In Final Fantasy X, the final boss fight take place in a series of pocket dimensions within a giant flying whale monster.
 * The last few parts of Final Fantasy XIII-2's amazingly long Final Boss sequence are in Valhalla.
 * Dynamite Headdy has a battle on an Amazing Technicolor Battlefield.
 * A rather weird example occurs in Xenosaga Episode 1, where the space station you're on inexplicably switches to a cloudy battlefield against the final boss.
 * In Kirby's Return to Dream Land the final battle indeed takes place in another dimension. In fact it's the name of the final level!
 * The Legend of Zelda: Majora's Mask. The final boss battle takes place in an alternate dimension within an alternate dimension. Or something to that effect. Also, inverted in Twilight Princess, when, after going through the last dungeon in an alternate dimension, during the boss battle Zant actually transports you to places in Hyrule visited previously during the game.
 * The final battle in Spirit Tracks is another example. In order to track down Malladus and Cole, you need to use the Compass of Light to follow them into the Dark Realm, a dimension of evil that they fled to immediately after Malladus' resurrection.
 * In the final battle in Skyward Sword, Link
 * A couple quest bosses in Runescape have you follow them into their own dimension to fight them.
 * End battle from Recipe For Disaster: the Culinaromancer, once you've gone and saved all the people he wanted to kill, you have to follow him and kill him and his tasty baked minions.
 * The Spirit Beast from Summer's End is only defeatable by going into the Spirit Realm.
 * In both Lunar Diplomacy and Dream Mentor you have to go to the Dream World to do the battles, though this is mostly for Dream Mentor as the battle Lunar Diplomacy is really very easy.
 * The Bonus Boss at the end of The World Ends With You is one, in Another Day. This is a Double Subversion: Another Day is a relatively normal Alternate Universe, but the fight takes place in Pork City, an amazing monochrome battlefield.
 * in Kingdom Hearts 358 Days Over 2. You are transported to in the Final Boss fight.
 * In order to fight Giygas in Earthbound, you have to hop in the Phase Distorter and travel possibly thousands of years into Earth's past. Also, once released from the Devil Machine, it's suggested that he's so large and distorted that he is an Eldritch Location dimension in and of himself.
 * Malygos in World of Warcraft is found in the Eye of Eternity, his private pocket dimension.
 * In Ultima I, you use a time machine to travel to the past and fight Mondain before he finishes creating the Gem of Immortality (which would make him unbeatable).
 * The Final Boss battle in Siren takes place in another dimension, and it fits this trope, but it's hardly an example of Amazing Technicolor Battlefield.
 * The Final Boss of Chrono Trigger, Lavos, is fought inside his first form's shell. His final form, however, is fought as both he and the party are thrown across corridors of time, with various eras flashing by at high-speed.
 * The final boss of the sequel, Chrono Cross, complements the concept by luring you into the darkness beyond time, where timelines discarded or destroyed by temporal paradoxes end up.
 * Freedom Force, where the Timemaster rips the heroes out of the time continuum.
 * Wario Land: Shake It! After you beat the boss' first form, he transports you to a battlefield in the clouds.
 * For some reason, the totally inexplicable final boss of Super Adventure Island 2 is some kind of one-eyed giant scorpion which you fight somewhere in space.
 * Lost Planet: While the rest of the game has you on the grounds of the planet,
 * In Baldur's Gate 2, you fight the final boss in hell. Which, yes, is another dimension.
 * And in the expansion you have the final showdown in Bhaal's old divine realm, the titular Throne of Bhaal.
 * The battle against Inferno in Soul Calibur II.
 * And Night Terror in 3. You fight inside Soul Edge itself.
 * The True Final Boss of Contra: Shattered Soldier.
 * Pretty much all of the Silent Hill games do this.
 * Wild Arms 2 has the final battle and final dungeon take place in the area where an alternate universe has started to encroach on the current one -- the final boss is this alternate universe.
 * Or rather, the boss that resolves the main plot. Shortly afterwards, you're abruptly thrust into a one-on-one fight with the real final boss, Bonus points for being taken out of one alternate universe to a seperate plane of existence.
 * Neverwinter Nights has you follow the final boss into a pocket dimension where her race has been hiding since the fall of their Empire. There's a bit of running round and slayage to do before you fight her, but only as a prelude...
 * Happens in the battle with Emperor Tachyon in "Ratchet and Clank: Tools of Destruction" due to an errant blast from the Dimensionator.
 * Sweet Home never actually states what the final region where you fight Mamiya is, but it isn't the rest of the mansion.
 * In The Legend of Spyro, the boss fight against Cynder takes place in a convergence of the planes.
 * In Robopon 2, the final battles take place in an unexplained, creepy location called the Robopon Graveyard. All you know is this is where the souls of Robopon go when they're scrapped, and the graveyard is totally filled.
 * In Persona 2: Eternal Punishment, the final dungeon is the Monado Mandala, part of the collective unconscious.
 * And in Persona 2: Innocent Sin, the prequel, the final dungeon is Xibalba, a spaceship the Mayans built.
 * The Knights Of The Nine quest line of Oblivion, has you fight the immortal Big Bad's spirit in another plane of existence to destroy him for good.
 * Ys III and V.
 * After you defeat Bowser for the third time in Super Mario Galaxy 2, just as you're about to pick up the Grand Star, he pulls you into a black hole, and you fight him one more time here. If it weren't for the fact that this phase is laughably easy, it would have been one of the best points of the game.
 * For the first stage of the final battle of Devil May Cry, Mundus transports himself and Dante into space.
 * Bujingai Swordmaster has the final boss Rei creating a new space and planet (which he later bisects) in order to create a proper battlefield.
 * The final boss of Radiant Silvergun is fought.
 * Touhou 12: Unidentified Fantastic Object has you fighting Byakuren in Hokkai, where she is sealed. Technically you got there in the previous stage, but close enough.
 * Since SuperNOVA, Dance Dance Revolution has had Amazing Technicolor Dance Stages. X2 uses a special abstract pink colored stage for its True Final Boss Valkyrie Dimension. And in fact, this is the first time this has been done.
 * Astaros in Robo Aleste.
 * R-Type does this a lot: the final level of each game invariably takes place in the Bydo home dimension. R-Type Final also had a second alternate dimension made of Tron Lines, and one of the possible final levels taking place as your ship time-travels 400 years into the future to stop humanity from ever creating the Bydo in the first place.
 * In Sword of Mana, Julius transports the hero and heroine into an alternate dimension with him after beefing himself up on Mana power.
 * Hellsinker does this in it's True Final Boss, we think.
 * Minecraft's final boss requires you to reach the dimension fittingly called "The End".
 * In Kingdom Hearts II, Xemnas takes Sora and Riku into the realm of nothingness for the final battle.
 * The final boss in Rune Factory Frontier is hidden in a seperate dimension called the Era of Disconnect so that it can't consume energy in the regular world.
 * In Super Fantasy Zone, the typical bright environment goes away after the Boss Rush, and the final battle is fought in the Shadow World.
 * Magisphere in Saga Frontier is a higher dimension designed explicitly for boss battles. In Red's game, many of the bosses are fought there (and it triples the power of BlackX enemies), while in Blue's game, Magisphere is reserved for the climactic duel between Blue and Rouge.

Movies

 * In Mortal Kombat, Liu Kang and Johnny Cage end up following Shang Tsung to Outworld for the final fight.