Master Core is a boss in Super Smash Bros. for Nintendo 3DS and Wii U. He is the Final Boss of the game's Classic Mode and Master Hand's true form when it is played on 5.1 intensity or higher. In addition, you must take the black path during the fight; taking the blue path will only have a fight with Master Hand. If playing on intensity 8.0 or higher, the black path will be only one available, meaning that a fight with Master Core is mandatory.
When Master and Crazy Hand appear on the field, they will have set amount of health (which varies on intensity). The player only needs to take out 60-70 health from one or both Hands. When this is done, Crazy Hand disintegrates while Master Hand's glove rips open, revealing the Swarm. If playing on an intensity 5.1 or above, it will only use its "Master Edge" form and "Master Shadow" form; starting at level 6.0, it will introduce its "Master Beast" form; and starting at level 7.5, its "Master Giant" form will appear. In the Wii U version, on intensity 8.0+ and defeating "Master Shadow", it will introduce another form; "Master Fortress".