The almighty Power Crystal of Ripple Star
The Power Crystal (not to be confused with the Crystal Shards, the pieces of the Power Crystal) is a mighty crystal artifact and is the priceless treasure of Ripple Star. Upon Dark Matter's assault on Ripple Star, Ribbon takes the crystal in hopes of protecting it. But as she flees the planet, three of Matter's Minions chase her through space. Ultimately, the Power Crystal is broken into approximately 100 small pieces and fall to many different planets around Ripple Star. Five friends (Kirby, Ribbon, Waddle Dee, Adeleine, and Dedede) then make it their goal to restore the power crystal to its former glory by collecting every Crystal Shard. As of now, the Power Crystal once again resides on Ripple Star.
While the Crystal's true purpose was never given, it is known that It is the only thing known that can purge Dark Matter from a body without using direct force. It can be assumed its purificatoin powers may have been the reason Dark Matter invaded Ripple Star in the first place; to prevent its use against him. Another commonly used-power in the game is the apparent ability to create portals (that can go as far as at least another planet), as seen in a variety of cut-scenes.
Its last known ability, and debatably most important, is to be used as a weapon that can fire small projectile presumably made of the crystal shards.