Miracle Matter

From Kirby - Wiki on Neoseeker

Miracle Matter appears in Kirby 64: The Crystal Shards as a boss of Ripple Star.

The battle against him is slightly time-consuming, and definitely very unique. Throughout the fight, Miracle Matter will change it's surface to represent different abilities that appear in the game. While it's surface is one ability, it only uses attacks of that same type. The bad thing is that you can only hurt Miracle Matter when you also have this ability. A smart thing to do is have a double ability. That way, you can hurt Miracle Matter during two of his types instead of only one.

Caution: Small spoiler ahead!
Miracle Matter is not actually the final boss of the game. When he is defeated he will explode, giving Kirby one huge Crystal Shard. If all 100 shards have been collected, then one Final Star planet will appear, revealing the real final boss: 0².