|“||When you get a skull key, you'll be warped to an area where the Skull Gang will attack. If you survive until morning or get the Treasure Chest, you'll be able to escape.”|
|— Daroach • Kirby Mass Attack instruction booklet|
A skull key is an item found in Kirby Mass Attack. It is a key that can be found in a random area throughout a stage. If one is obtained, the player's Kirbys are sucked in by a skull-shaped portal that leads to a dark area. A large group of Skullys then appears, ambushing the group. They attempt to snatch the heroes, and with their great numbers, they can be devastating to a small squad of Kirbys. Individually, however, the Skullys can be defeated with just a few Kirbys.
The way to escape from the Skull Gang is by defeating the red Skully that holds a skull chest. If it is destroyed, the chest will fall to the ground and the other Skullys will fly away and disappear. Alternatively, the Kirbys can wait until a rooster crows, signaling the morning and prompting the Skullys to flee.
Using the skull key, the skull chest can be opened. Once opened, the player will receive a medal. If it has been previously obtained, fruit will come out of the chest instead. After the reward is received, the portal will come back, taking the Kirbys back to where they picked up the key.