Boss Remix

An existing theme (often calm, ambient music or otherwise unsuited for fighting) is rearranged for a boss fight or The Very Definitely Final Dungeon. Generally faster paced and instrumental.

See also Battle Theme Music. May overlap with Crowning Music of Awesome. Common when we have a Theme and Variations Soundtrack. Not to be confused with a remix that is totally boss.

Action Adventure

 * Zelda II the Adventure of Link created a remixed version of the Temple (dungeon) background music for use in the Great Temple (last dungeon).
 * The Legend of Zelda did this with its creepy final dungeon music.
 * The Legend of Zelda the Minish Cap has this in the battle against Vaati's final form (after the castle is collapsing).
 * In The Legend of Zelda Twilight Princess, the fight against is a remix of Ganondorf's theme and  . Very disconcerting.
 * The dungeon proceeding that fight also plays a remix of Ganon's Theme and the  theme from The Legend of Zelda a Link To T He Past, to pretty much the same effect.
 * Each fight against consists of techno remixes of past bosses' themes.
 * And bongos!
 * The Legend of Zelda Phantom Hourglass has a remix of for the final battle, with snippets of Bellum's Theme mixed in to emphasise.
 * And just prior to that, the maritime battle with the Bellum-possessed Ghost Ship is accompanied by a sinister remix of the overworld music.
 * In Wind Waker, the "stormy night" theme was a combination of the the overworld theme and Ganondorf's theme.
 * The Legend of Zelda Spirit Tracks has a remix of for the first phase of  followed by an epic remix of the  in the second phase, which itself is a remix of the game's main theme.
 * Also, a panicked remix of Zelda's Lullaby, when.
 * The Theme Music Power-Up during boss battles in TP is a remix of the Hyrule Field theme. Also, some bosses(especially Stallord) use remixes of "Dinosaur Boss Battle" from Ocarina of Time.
 * Each phase of the The Legend of Zelda Majoras Mask final battle uses a different remix of Majora's Theme.
 * The boss fights against Brainwashed and Crazy Richter Belmont in Castlevania Symphony of the Night and Richter's ghost in Portrait of Ruin are both set to remixes of Richter's theme from Rondo of Blood. Also used in Castlevania: Aria of Sorrow, where the stage music "Heart of Fire" from the old NES game was turned into an awesome boss theme.
 * In Ratchet and Clank Up Your Arsenal, the battle theme for Courtney Gears is a remix of her music video "Death to Squishies".
 * La-Mulana is all over this trope. Each boss theme contains elements of the music for the area in which they are located. Also, the final battle is a remix of the Surface theme with parts of the Guidance Gate thrown in.
 * Nie R has the Song of the Ancients, a relatively mellow song which appears several times throughout the game. It reappears during some boss fights with a darker, more combat-suited tone, most notably during the fight with the Betrayers,
 * ''Kid Icarus Uprising has Boss Theme 2, which plays during the battle with Medusa . It has part of the underworld theme from the original game, as well as Ominous Latin Chanting.
 * Also, Leitmotif is remixed into both the music for several levels and his battle music.

Action Game

 * In the original Devil May Cry, the final battle with Nelo Angelo incorporates sections of Sparda's theme, heard in the game's introduction.
 * In Onimusha Dawn of Dreams Munenori Yagyu has his own battle theme. During the final battle against Jubei it becomes a remix of Jubei's and his own theme.
 * The final boss of No More Heroes, uses the Crowning Music of Awesome "We Are Finally Cowboys", a remix of the main theme. In the sequel, when you do get to use  in his boss fight against, the Golden Brown remix of "We Are Finally Cowboys" plays during the fight.
 * In the third installement of God of War, The final boss battle with Zeus has this song that contains sections from Zeus Wrath Divine from the first God Of War and The Isle Of Creation from God Of War II. Both remixed themes appeared in final boss battles of their respective games.

Beat'Em Up

 * In the arcade version of Double Dragon II, Willy's battle theme is a sinister remix of the title theme. The final battles of Double Dragon 1 and Super Double Dragon reused the title theme straight. The main boss theme in the NES version of DD II is a remix of DD 1 Arcade's boss music. Inversely, Burnov's theme from the arcade version got used for the Trap Room level in the NES version.

Fighting Game

 * The music on the Final Destination stage in Super Smash Bros Brawl (where, as the name implies, the final battle takes place in Classic mode) is a Boss Remix of the title theme.
 * As is the Boss Rush, where it is a remix of Melee's menu theme. It's not as intense as the Melee Battlefield's own boss remix of the theme, though.
 * The "regular" boss fights during the Subspace Emissary mode in Brawl also feature a remix of the game's main theme. That song comes up a lot throughout the game.
 * One of the alternate songs on Brawls Final Destination stage is a boss remix of Melees opening theme.
 * Going far back to Melee itself, its Final Destination stage offers us a boss remix of the first Smash's credits theme. A special arrangement for Giga Bowser also exists.
 * Cruel Brawl has its own boss remix of Brawl's main theme, only played in that mode.

First-Person Shooter

 * In Perfect Dark, final battle's music features the game's main theme.
 * In Perfect Dark Zero, the music for the second and last fight against Maihem is a combination of the game's main theme and Maihem's theme. The music for the final showdown begins with a remix of the original Perfect Dark theme.
 * Not technically a boss music, but in Turok 2, the River of Souls theme is an extended remix of the Title Theme Tune. There's also a more frantic remix of the title theme in the sound test, as if it were meant for a boss battle, but it doesn't appear anywhere in the game.

Light Gun Game

 * In the Time Crisis series, Wild Dog's battle theme is an intense remix of the series' main theme. The second game rearranges "Deadly Fight"(Diaz's theme) for the final battle with the Doomsday Device.
 * In House of the Dead 2, the Magician's theme is remixed with an Ominous Pipe Organ intro.
 * The Magician's theme itself is a remix of the series theme.

Mecha Game

 * Zone of the Enders: The Second Runner has "Air Fight," played during an epic battle between Jehuty and the BAHRAM fleet (and one of few [sane] times you can use your Wave Motion Gun in combat). It's a rearrange of the opening song, "Beyond the Bounds."

Platform Game

 * Donkey Kong 64 used a fast-paced (synth) orchestral arrangement of the level's theme (many could qualify as ambient in their standard rendition) for the boss of each stage. "Boss remix" has been used as a descriptor for fan made arrangements done in such a style.
 * The boss theme and Klubba's theme in Donkey Kong Country 2 are both remixes of the title theme.
 * Banjo-Kazooie has the main layer theme rearranged for the final boss theme.
 * The sequel has one of these for each individual world's theme, with the exception of the last two. The penultimate level, Cloud Cuckooland, features a boss remix of the music.
 * In the first game, the Final Battle soundtrack is a combination between Gruntilda's theme, game's main theme, Rusty Bucket Bay and Mad Monster Mansion. In Banjo-Tooie, also, the final battle is a new melody, but features Gruntilda's theme. Banjo-Kazooie: Nuts & Bolts' challenge music is also a remix of Gruntilda's theme, and the scrapped final challenge music (which is part of the game's soundtrack) is an epic combination of Grunty's theme remix and Banjo-Kazooie main theme.
 * In Wild9, the last level has the same music as the first, only in a lower key and extended.
 * The final boss fights for Sonic the Hedgehog 2006 and Sonic Unleashed both use orchestral arrangements of their respective games' main themes.
 * In the former, the leitmotifs for the four villains are constantly rearranged for their cutscene and boss battle appearances. This is retained for Eggman in the latter.
 * The Final Boss themes for the first and second Genesis games were remixes of their respective main boss themes.
 * Sonic Colors does the orchestral remix of main theme for the second part of the final boss.
 * Sonic & Knuckles remixed Sonic 3's Act 2 Boss theme for its Act 1 bosses.
 * The fan-made Sonic Robo Blast 2 inverts this: the theme for the fourth zone is a remix of the boss theme.
 * The Neo Geo game Top Hunter: Roddy & Cathy use a remixed version of the current level theme whenever you fight the recurring Miniboss.
 * The Battle Windows/Computer Virus in Kirby Super Star has an 8-bit version of the main boss theme.
 * In Kirby Super Star Ultra, Dyna Blade, Wham Bam Rock and the remake-exclusive Wham Bam Jewel have a boss remix of the Castle Lololo theme from the first Kirby game, Kirby's Dreamland, instead of the usual boss theme. In the same game, Masked Dedede also has a different arrangement of regular Dedede's theme.
 * Inverted within Ultra as well - Dedede's boss theme is remixed into a Solemn Ending Theme for the credits sequence after Masked Dedede.
 * Wario: Master of Disguise has Count Cannoli's slow refined theme become fast and loud when he breaks out his giant robot. Carpaccio's theme also seems remixed for his fights.
 * Klonoa 2: Lunatea's Veil has what can best be described as a reverse boss remix- the boss theme for is remixed into a calmer, somewhat emotional theme in the cutscene following the fight.
 * Viewtiful Joe's final boss,, uses a remixed version of Captain Blue's theme, which was heard in the sub-boss fights with him early in the game.
 * Another Joe uses a remix of "Joe the Hero", Joe's own theme (as heard in the first level).
 * Mega Man ZX: The final area theme is a remix of the "Sadness" theme featured in cutscenes very early in the game.
 * The Wily Stage boss theme in Mega Man 3 is a faster remix of the "Wily Stages 5 & 6" theme.
 * Bass's Boss theme in Mega Man 8 & his shop theme in 10 are remixes of his 7 theme.
 * The boss themes in Ghosts N Goblins were frantic remixes of the main level themes.
 * Super Ghouls and Ghosts follows suit, although the boss remixes for levels 3 and 5 were obviously switched for some reason.
 * The miniboss themes from Yoshis Island are remixes of their introductory theme musics, probably to fit the fact that all but one are ordinary enemies turned huge by Kamek's magic (the one that didn't had Kamek shrink Yoshi and Baby Mario instead, who both then get eaten by said boss).
 * Super Mario Galaxy and Super Mario Galaxy 2 actually both play this straight with Bowser Jr., whose pre-battle themes actually get remixed into those of "Airship Armada" from Galaxy, and "Boomsday Machine" from Galaxy 2, respectively. Curiously enough, parts of his battle theme sound an awful lot like those of Primal Dialga's, as mentioned below.
 * Inverted with Bowser at the end of the first game however, where the final confrontation against him is actually set to techno music, but after he is defeated the first part of his battle theme plays again, but this time 14 more notes are added before the choir, (his final boss theme starts with the choir) and then the Sun in which Mario and Bowser fought inside for the final battle collapses and implodes, destroying the entire universe in the process. The final boss theme as a whole (including the 14 notes before the choir at the start) can be heard in the game's official soundtrack, however.
 * There's also Squizzard's battle theme from Galaxy 2, which features a remix of the Fire Flower theme.
 * The  Bowser theme from New Super Mario Bros Wii is actually the main theme played on an Ominous Pipe Organ.
 * In Psycho Waluigi the final boss theme against  is a remix of the Waluigi Pinball theme mixed with  theme. It sounds creepy and quite frantic, perfect for the character that you're fighting against.

Role Playing Game

 * Grabbed By the Ghoulies' boss theme is a remix of game's main theme.
 * The final battle in Baldurs Gate.
 * Skies of Arcadia has an arrangement of the main theme when you are winning the final battle.
 * Several of the final bosses in Saga Frontier had this most noticeable is the final boss theme in Red's Story.
 * Persona 3 has a boss remix of the main theme as you fight the final boss. And a battle rendition of, for the penultimate boss fight.
 * In The Answer portion of Persona 3 FES, the final battle theme "Darkness" is a boss remix of the ending theme, "Brand New Days."
 * And Persona 4's final boss theme, "The Genesis", starts off as a dramatic, brooding piece, but it builds up towards a climax with an orchestral fanfare of "I'll Face Myself", one of the game's major Leitmotifs (which also happens to have a Boss Remix), finally building up to a triumphant finish with an instrumental version of "Reach Out To The Truth", the game's main battle theme (and arguably more the game's theme song than "Pursuing My True Self").
 * Persona 3 Portable has "Danger Zone," the female protagonist's boss theme, which is a remix of the game's new opening theme, "Soul Phrase." The normal battle theme, "Wiping All Out" is something of a battle remix of "Soul Phrase" as well. In fact, a good deal of the female protagonist's new BGM consists of arrangements of "Soul Phrase"- similar to how several pieces of the male protagonist's BGM consist of "Burn My Dread" arrangements.
 * Typically occurs in the Paper Mario series, as before each boss encounter a theme that is specific to the boss plays, which is then remixed for the battle. This is most obvious with bosses whose themes play multiple times before the actual fight, such as Bowser, Grodus, and Count Bleck.
 * Several times during Super Mario RPG, a town is taken over by a Boss, and the music changes to indicate the trouble. When you face the boss, the fight is accompanied by a boss remix of the 'trouble' music.
 * The battle against Smithy's first form is also a remix of the 'trouble' theme, albeit with all sorts of mechanical sounds added in, along with an Ominous Pipe Organ.
 * The Climax Boss fight against Cackletta in Mario & Luigi: Superstar Saga is accompanied by a boss remix of her theme mixed with the "panic" theme.
 * In Mario & Luigi: Bowser's Inside Story, Giant Bowser Battles are accompanied by a boss remix of Bowser's theme.
 * The last battle in The World Ends With You uses a remix of the game's main theme, "Twister", that is unique to that fight - unlike all the other boss fights in the game, which use music from the game's regular selection.
 * The English version of Someday plays only on the boss battle with Minamimoto; every other time you hear it it's the Japanese version...
 * The three main Organization XIII battle themes in Kingdom Hearts II (The 13th Struggle, Dilemma, and Reflection, respectively) all feature some element of the song Another Side, which was used in the secret ending to the first game and is the origin of Organization XIII's theme. This also applies to Marluxia's first and third battle themes, Graceful Assassin and Lord of the Castle.
 * And for a more obvious example, the Final Boss theme of the original Kingdom Hearts game, "Guardando Nel Buio", is a remix of the End of the World's battle theme "Fragments of Sorrow", which in turn is a remix of the song "Destati" from the very beginning of the game.
 * And for an even more obvious example, the Final Boss theme of Kingdom Hearts II, "Darkness of the Unknown," features a remix of itself: the track is actually broken up into 3 looping portions in the game (which correspond to the last boss), with the last third being a slow remix of the second.
 * Not to mention "The Other Promise," used for the fight against Roxas in the second game's Updated Rerelease, though it's just as melancholic as his normal theme.
 * in 358/2 Days has a remix of said character's theme that is somewhere between "The Other Promise" and your usual Kingdom Hearts boss theme in its pace.
 * True to the series, Birth By Sleep includes several boss remixes:
 * Vanitas' two battle themes are remixes of
 * "Dismiss", the theme of the True Final Boss, is a remix of "Fragments of Sorrow", this time incorporating aspects of, and "Destati" into it.
 * Inverted with Terra's theme, which is a slower version of "Rage Awakened", which plays during the Bonus Boss fight of Kingdom Hearts II Final Mix..
 * "Master, Tell Me the Truth", the music for the Armor of the Master fight in Final Mix, is a remix of The Land of Departure battle theme with cues from Terra, Aqua and Ven's themes included.
 * "Forze dell'Oscurità" is a combination of the battle themes for Ansem and Xemnas, and is appropriately used for the battle against No Heart,.
 * In Parasite Eve, Eve's boss battle theme, "Influence of Deep", is a remix of her opera singing from the start of the game, with techno music, some instruments and an Ominous Pipe Organ tossed in for good measure.
 * Treasure of the Rudra has a different Boss Remix depending on which character's story the player is currently on, with the remix being of the character's overworld theme.
 * The Tales Series has a fondness for this.
 * Only recently. Meaning of Birth and Fury Sparks are the only ones that qualify. Irony of Fate is an inversion in that it's a boss battle theme remixed as a sad song when.
 * Tales of the Abyss does this more than once. The final two battle themes both contain arrangements of the menu music, and Finish the Promise includes (quite fittingly) a rather epic quotation of the Grand Fonic Hymn.
 * Further back than those, Tales of Symphonia had 3 battles with remixes of character themes. The End of a Thought, which played during, It Can Waver And Fight, played during most fights with the Big Bad (as a remix of his theme), and Final Destination, the final boss theme, which is another remix of the Big Bad's theme.
 * The final dungeon in the Massive Multiplayer Crossover action RPG Dengeki Gakuen RPG: Cross of Venus uses a fast-paced, dramatic and more heroic remix of the game's opening theme, "Odyssey".
 * Both Baten Kaitos games remix the awesome song "The True Mirror" (the first game's normal battle theme) for several boss fights. Most of the plot-important bosses in the first game get an electric guitar version, and in Origins gets an orchestral version,.
 * The final map theme for Soul Nomad and The World Eaters is a faster version of the title music with Ominous Latin Chanting. Feinne's theme is also a variant of the title theme.
 * Super Paper Mario uses remixes the theme for Merlee's Mansion for your fight with Mimi, Count Bleck's Leitmotif for your final battle with him, and the themes of for.
 * The final boss theme in Paladins Quest (aka Lennus 1) has a remixed version of the main villain's theme along with the game's main battle theme.
 * The boss battle theme of Megaman Battle Network 5 is a remix of the normal random encounter theme.
 * The final boss themes of most games in that series are remixes of the normal boss theme.
 * Pokémon makes use of this for the Frontier Brains of Emerald and Platinum by heavily remixing the Battle Frontier themes of their respective games.
 * It's worth noting that the Platinum Frontier Brain Battle is a remix of BOTH Emerald and Platinum Battle Frontiers.
 * Also the Galactic commanders have a remixed version of the grunts' battle song. And Dialga/Palkia song is the remixed song of the Sky Pillar.
 * When fighting a Legendary Pokemon in FireRed/LeafGreen, the Wild Battle theme goes up a pitch.
 * The Champion battle music from Pokémon Gold and Silver (and Heart Gold and Soul Silver) is a remix of the main theme.
 * The Gym Leader Theme in Diamond,Pearl,& Platinum was remixed for the Elite Four
 * Pokémon Mystery Dungeon: Explorers of Time/Darkness/Sky features a mix between the game's main theme and the Leitmotif associated with time itself for the final battle against Primal Dialga. And it's awesome.
 * The original Champion Battle theme from Gen 1 gets remixed for the final Battle Subway fight in Gen 5. Practically a Recurring Riff. It might not count since Champion Battle is (obviously) a boss theme itself.
 * Also in Black/White, N's Theme gets louder, faster and generally more epic in your last battle with him.
 * In Mother 3, a small part of Dry Guys is from one of the overworld themes. Also,.
 * In fact, Mother 3 reuses leitmotifs and riffs all throughout the game. Most of the battle themes have a secondary version (which are designed to catch out players who know how to take advantage of the game's 'Rhythm Battle' system), which is essentially the same theme but with a change of some kind in the rhythm at certain points in the tracks (whether through a deliberate glitch in the music to trip the player up, being a faster/slower version of its other version, or even altering the time signature between versions), so boss battles with familiar battle themes can generally be assumed to use the more difficult version. For instance, compare, with the aid of the heartbeat provided when you put an enemy to sleep, how easy it is to tap along between Mr Passion's first battle theme against the theme for the optional rematch against him.
 * Golden Sun: In the first game, the final battle with Saturos and Menardi is accompanied by a remix of their theme. The same goes for the second game, where Agatio and Karst's theme becomes their battle music.
 * MARDEK: While regular bosses use the standard piano boss battle theme, major antagonists have specific Boss battle themes when fighting them; fighting Muriance the bandit chief changes his main theme into Muriance Battle, the World's Saviours get their theme changed into Saviours Battle, etc. Seems to be a favorite tactic of Pseudolonewolf to reuse certain things from each song...which makes it epic.
 * Both the "Theme of Chaos" and "Theme of Law" from Shin Megami Tensei Strange Journey are given bombastic remix treatments for the endgame battles with.
 * Final Fantasy I only had the one battle theme which was used from your first fight with imps all the way to the Big Bad. However, for the Updated Rerelease of the game on both the Game Boy Advance and the PlayStation, boss fights had a rearranged version of the basic battle theme (which was already remixed from the 8-bit original).
 * Final Fantasy II uses remixes of the Castle Pandaemonium theme for both its normal battle theme and its boss battle theme.
 * The Mysterious Girl's battle theme in Final Fantasy IV the After Years is an intense remix of her Leitmotif.
 * In Final Fantasy V, Exdeath's battle theme (before he goes One-Winged Angel) is a remix of his character theme.
 * Dancing Mad from Final Fantasy VI. All sorts of recurrent themes and motifs from other songs along the game get thrown into it, most prominently "Omen", "Catastrophe", as well as Kefka's Leitmotif and "Fight to the Death" (the music used for the fights against Ultima Weapon and the Warring Triad.)
 * In Final Fantasy VII, the final battle with JENOVA: SYNTHESIS has a tense remix of the standard Random Encounter theme.
 * Both "Birth of a God" and "One-Winged Angel" (which play during the first and second parts of the Final Boss fight, respectively) incorporate Sephiroth's original character Leitmotif, "Those Chosen by the Planet".
 * Final Fantasy IX has "Protecting My Devotion," a battle arrangement of Beatrix's theme, "Rose of May," that plays when she and Steiner defend Alexandria from an enemy attack at the beginning of Disc 3. Kuja's theme is remixed as "Dark Messenger" when he's fought at the end of the game.
 * In Final Fantasy XII, any fight against a major character from the Archadian Empire would almost always have a remix of the Empire's Theme playing during the battle.
 * "Fusion, descent" from Final Fantasy Crystal Chronicles is a boss remix of the main theme.
 * Phantasy Star II's boss theme ("Hard Place") is a techno remix of the title theme ("Phantasy").
 * In Ys: The Ark of Napishtim, the Ark Leitmotif (heard in "Defend and Escape" and "Revival of the Great Ark") gets an epic remix in the second half of the Final Boss battle.
 * Chrono Trigger: "World Revolution"
 * Eternal Sonata has, of all things, a remix of

Shoot'Em Up

 * Axelay does this for each stage: The bosses' themes are darker and/or rearranged versions of the level theme, usually in a style that suits the boss. For example, the theme for the Humongous Mecha boss is more electronic than the stage music.
 * Much of the music of Ikaruga is just remixes of Ideal. But when you hear the same theme remixed during a boss fight, you know something nightmarishly difficult and impossibly epic is about to happen.
 * In turn, the Stage 2 boss theme, "Recapture", is a darker arrangement of "Trial", that stage's main theme.
 * Ray Crisis selects a musical theme based on what level you start with, and all subsequent level and boss musics are variations of that theme.

Simulation Game

 * The theme for Ace Combat Zero: The Belkan War, which appears in snippets and snatches here and there across the soundtrack, gets the full rundown in the final boss fight. A variant is "Alect Squadron" from Skies of Deception, starts with a guitar solo and brings the titular piece in partway through.
 * The Final Boss theme of Trauma Center: Second Opinion is a remixed and faster version of the main menu theme.

Stealth Game

 * Metal Gear Solid: Twin Snakes contains a remixed version of Psycho Mantis' mind control music for his boss battle. Personally this troper's favourite boss battle music in a video game.
 * Metal Gear Solid 4. The first part of the final boss has a remix of Encounter from the first game.

Survival Horror

 * Haunting Ground has an interesting version of this. Each of the three stalkers have their own Leitmotif when chasing you. During each of their boss fights, their particular motif is remixed with a sort of "template". This template remains the same for the first three three bosses, making their themes sound very similar. However, there is a part of the track that distinctively belong to the particular boss (e.g. Daniella's static interferences).
 * Alexia's battle themes in Resident Evil Code Veronica were orchestral remixes of "Alexia's Lullaby/Berceuse", with a One-Woman Wail as the melody. William in Resident Evil 2 and Nemesis in Resident Evil 3 also use remixes of their themes for each of their mutations.

Third-Person Shooter

 * Boss theme of the videogame adaptation of Terminator Salvation is a remix of Terminator's main theme.
 * In Megaman Legends when you face the final form of the big bad the music is changed to something completely different from the first forms theme. In the case of the first game the tempo was simply increased in the second game the theme was changed entirely.
 * In the original Syphon Filter, the themes for the battle with Aramov is a remix of the Subway Battle Theme Music, the Chopper battle music is a remix of Girdeux's battle theme, and Rhoemer's battle theme is a powered-up remix of the main theme. Also, some of the "boss" themes in Omega Strain are remixes of previous action themes.
 * The first phase of the Final Boss in PN 03 uses a faster, more sinister remix of the main boss music, but unfortunately it's a Wasted Song, as the first form can be beaten in less than 15 seconds.

Turn Based Strategy

 * Fighting an enemy you can recruit in Fire Emblem: Genealogy of the Holy War has a unique battle theme, a variation of (appropriately enough) the recruitment theme.
 * Additionally, the Black Knight, Idoun, and Lyon all have a boss remix of their Leitmotif.
 * As do, , and in Radiant Dawn. Caineghis has one as well, but luckily for you he's on your side the whole game.
 * Variation: In Heroes of Might and Magic 5, siege battles are accompanied by a remix of the city´s theme.
 * Many character themes in Luminous Arc 2 are remixed into boss battle themes when fighting them. The aptly named "Rosetta Rosso" theme is remixed into "Rosefall;" Fatima's "Shadow Frost Witch" is remixed into "The Dark Wings, Hugging to Freeze;"  "The Ruler" is remixed into "The Dictator's Force;" and lastly,   theme "Black Flames" is remixed into "Raging Flames".
 * Even the first Luminous Arc has at least one boss remix. The final boss theme "Believe in Yourself" contains a partial remix of "Theme of Luminous Arc." "Existence" may have been remixed as well into the boss theme, but it's difficult to tell.

Visual Novel

 * In the Ace Attorney series, as the trial approaches its climax, the normally calm theme that plays during cross examinations will be replaced with a faster and more frantic remix.
 * In Trials and Tribulations, when you're presenting the very last piece of evidence, a remix of the Cornered theme from the first game will play with an added drum track.

Anime

 * Tengen Toppa Gurren Lagann has one with a One-Woman Wail.

Film

 * Interesting example in Advent Children: Tifa and Loz fight in Aeris's church to a piano version of the FFVII battle theme.

Web Comics

 * Homestuck: The standard "Harlequin" theme is remixed into "Harleboss" for John's battle against the Crude Ogres.
 * And then