Master Core

Master Core is the final boss of the Classic mode in Super Smash Bros. for Nintendo 3DS, along with Super Smash Bros. for Wii U; it can only be fought on intensity levels 5.1 and higher. During the final battle between the player and both Master Hand and Crazy Hand, once Master Hand loses a portion of his stamina, Crazy Hand leaves, and Master Hand's glove rips open and reveals Master Core.

Master Core is hidden under a mass of black particles called Swarm, that take on a variety of different transformations and forms during the battle, each form doing a different attack. The forms that Master Core uses include a humanoid known as Master Giant, a monster known as Master Beast, a group of swords known as Master Edges (Master Sabres in the PAL version), a clone of the fighter known as Master Shadow, and the true Master Core itself.

The initial form of Master Core depends on the intensity level. By setting the intensity to 7.5 or higher (7.0 or higher in Super Smash Bros. for Wii U), Master Core will start out in its Master Giant form. Setting the intensity to 6.0-7.4 (6.0-6.9 in Super Smash Bros. for Wii U) will have Master Core start as Master Beast. Finally, setting the intensity to 5.1-5.9 will have Master Core start as Master Edges.

Master Shadow is always fought after Master Edges, and it is a clone of the fighter, down to the fighter's customizations, which include any active equipment and custom specials. The clone begins as being larger than the fighter, but it shrinks as it takes damage. The player either has to KO Master Shadow or fully deplete its stamina to defeat it.

In the Wii U version, an exclusive form known as Master Fortress appears after beating the first four forms, but only when the intensity level is set to 8.0 or higher. The player is given 3 extra minutes, along with a Heart Container, and must travel though a maze made from the Swarm to destroy various weak points. Master Fortress only appears in Solo mode, however, so it is never encountered at all in Group mode.

Once the Swarm is defeated, the black mass disappears, and reveals Master Core's true form, a colorful ball resembling a Smash Ball. In this state, Master Core is completely vulnerable, though if it is not destroyed within 45 seconds, it rises and starts to attack the player by emitting waves that instantly KO the player if hit before it automatically self-destructs.