Chaos Eternity

"Bleah hah hah hah hah. You cannot stop me now, for I am Chaos Eternity!"

Cackletta--Paper Mario: The Next Chapter.

Chaos Eternity is Cackletta fused with the Chaos Gem to create one symbiotic being.

Biology
Chaos Eternity was originally a beast that was supposed to become the protectors of the heralds, but it never came to be. Cackletta's form of the beast is just a shadow of the true beast.

The defeat
After Mario defeated Chaos Eternity, it said that it left one more surprise for the heroes, but this "surprise" was stopped.

Trivia
The name Chaos Eternity itself means Discord Forever, meaning that Cackletta planned to plunge all dimensions into chaos forever.