Master Core is an optional boss in at least the 3DS version of Super Smash Bros. 4. It is formed from the fusion of Master Hand and Crazy Hand on high difficulties, should the player choose to fight them both.
On high enough difficulties (the exact range being currently unknown), once the Hands lose approximately 75 HP, they will leave the battle and merge into the Master Core entity. Master Core is a black mass of particles that takes on varying forms based on the difficulty and battle progression. It has HP, like other bosses, but it is hidden from the player.
Forms
Master Core begins the fight in a given form based on the difficulty. Once a form is defeated, it progresses to the next one.
Note that all names for the forms are currently unofficial.
Sapien
The Sapien form is a large humanoid creature. It appears as Master Core's starting form on only the highest difficulties. Its attacks include firing energy balls from its forehead and grabbing players with its hands or its forehead. It is capable of moving the stage vertically to try and get players hit by its other attacks.
Scorpion
The Scorpion form appears on middle-high intensities, or when the Sapient form is defeated. It can fire spikes out of the ground, chomp at the player from the background with its large jaws, and do a full-body stomp that causes the stage to tilt for a brief moment.
Sabres
This form can be encountered first at middling difficulties, or when the Scorpion form is defeated. It appears as a group of five swords, one larger than the others. The swords can fire homing projectiles and slash at the player in varying formations. It appears that any of the swords can be damaged equivalently.
Simulacrum
In the penultimate phase, Master Core forms a copy of the player's character, slightly larger in size but otherwise equal. This form can be defeated either by depleting its stamina or by KO'ing it as with any normal character. There does not seem to be a difficulty where this is the only form fought.
Source
Once the Simulacrum is defeated, the Core itself appears in the center of the stage, and its percentage is now visible (starting at 0%). The player must now simply rack up its damage to KO it; there appears to be no challenge in doing so, as it has no attacks and the clock is stopped. If the knockback of an attack does not KO the Core directly, it simply returns to the center of the stage.
Gallery
Fusing from Master Hand and Crazy Hand.
Trivia
- During the battle the background music will occasionally go silent and a few quick beeps will play. Those beeps are morse code and spell out "Master Core".