Subspace is a stage that appears in the Subspace Emissary. The player initially takes control of King Dedede, Ness, and Luigi. As the player travels through the Subspace, they will collect trophies of the other characters that were made into trophies by Tabuu.
As Ganondorf hails Master Hand, he realizes that Tabuu is controlling Master Hand with the mysterious Chains of Light, stabbed into all five knuckles and in the middle of the back of the hand, and rushes at him using Dark Dive, but Tabuu smashes him back effortlessly. As Ganondorf falls, he breaks the Chains of Light and frees Master Hand, who rushes at Tabuu. Unfortunately, sheer rage was not enough and Tabuu defeats Master Hand just as easily.
Meanwhile, the heroes infiltrate the Susbspace area, and are anxiously waiting to storm into it. They rush into a scene in which Tabuu uses his Off Waves to turn the heroes into trophies. As the camera scrolls around, everyone is in trophy form. A satisfied Tabuu forms the Great Maze as his kingdom.
Back at King Dedede's castle, Luigi, Ness, and King Dedede are stuck in trophy form. King Dedede's brooches, however, revive Luigi and Ness. After being released from trophy form, they decide to save Dedede, and the 3 heroes set off to find the rest of the gang.
After recovering all the trophies in the stage, Dedede revives Bowser, but he tries to attack them, so Dedede engages him. After the fight, Dedede revives Bowser again, and shows him Tabuu. Bowser lowers his head and follows them.
After this, Bowser, Luigi, Ness, and King Dedede join the player's team, Luigi and Ness are unlocked for other game modes, All Fighters that the player collected will return.
Not all characters are collected by King Dedede, Ness, or Luigi. Kirby is in another area of Subspace and is revived by the Dedede badge he took from Dedede's castle. Even if the trophies are touched by the player, the life stock will not increase and they will not be playable until after the level.
- Samus - Before the first door the player enters.
- Pit - After Samus, go into door and go up to the first door on the right. Enter and revive Pit.
- Falco - See Pit.
- Lucas - After Falco & Pit, go up top to get Lucas' Trophy. Be careful of Trowlons here, as they may lift it up if the trophy is in range.
- Ike - Go left to find Ike. This trophy is missed quite often.
- Donkey Kong - Step on the gold platform and jump to the Donkey Kong trophy.
- Pokémon Trainer - Go to the top and enter a door.
- Pikachu - After Pokémon Trainer break a bomb block near the left to reveal Pikachu. The player has to be quick to grab the trophy before the blocks below them give away.
- Marth - Continue to go right and up and grab the Marth trophy.
- Fox - After Marth go left and enter the door.
- Olimar - See Fox.
- Mr. Game & Watch - After Olimar, go through the right door, head right and hit the bomb blocks.
- Diddy Kong - Go through the door after finding Mr. Game & Watch and grab Diddy on the left.
- Captain Falcon - After snagging Diddy swipe the Captain on the right.
- Mario - He is the last trophy collected with the three heroes.
- For the first part of the level, Step: Subspace plays.
- In the second half of the level, Step: Subspace Ver. 2 plays.
- During the fight against Bowser, Giga Bowser (Melee) plays.