Master Core

Master Core is the final boss of the Classic mode in Super Smash Bros. for Nintendo 3DS; he can only 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 Blades, a clone of the fighter known as Master Shadow, and the Master Source form. In the Wii U version, an exclusive form known as Master Fortress, will appear after beating the former forms, minus the Source, where the player must travel though this new form to destroy various pieces.

The initial form of Master Core depends on the intensity level. By setting the intensity to 7.5 or higher, Master Core will start out with the Humanoid form. Setting the intensity to 6.0-7.4 will have Master Core start as the Monster form. Finally, setting the intensity to 5.1-5.9 will have Master Core start as the Swords form.

The clone is always fought after the Swords form, 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 the clone or fully deplete its stamina to defeat it.

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 in a certain time it rises and starts to attack the player by emitting waves that instantly KO the player if hit before it automatically self-destructs.