The Crystal is an item in Kirby 64: The Crystal Shards. It is a large piece of diamond-shaped crystal located in the palace of Ripple Star, the planet of the Fairies. Upon noticing the invasion of Dark Matter on Ripple Star, Ribbon takes the crystal in hopes of protecting it. But as she flees the planet, three Dark Matter chase her through space.
During the chase, the Crystal is broken into 74 pieces (called Crystal Shards) which fell to many different planets around Ripple Star. Five friends (Kirby, Ribbon, Waddle Dee, Adeleine, and King Dedede) then make it their goal to reconstruct the Crystal by collecting the Shards. After the events of Kirby 64: The Crystal Shards, the Crystal once again resides in Ripple Star Palace.
While the Crystal's true purpose was never given, it can purge powerful Dark Matter from a body without using direct force. It can be assumed its purification powers may have been the reason the Dark Matter invaded Ripple Star in the first place; to prevent its use against their forces. The incomplete Crystal can also create inter-planetary portals, as seen in the cut-scenes. Lastly, Ribbon can use it as a weapon; it fires small projectiles, presumably made of the Crystal Shards.