Zygarde

Zygarde is a dual-type Dragon/Ground Pokemon. It is not known to evolve into any Pokemon though it has several different forms.

Biology
Zygarde 50% has a serpent-like body with a green and black pattern on it. There are black frills on the back of its head like a frilled lizard. Its eyes comprise four green hexagons like the compound eyes of an insect. More green hexagons are on the front and back of its frills. These hexagons glow in certain patterns like a computer processing information. Its tail is flat and is black on top and green on the bottom. Its tail ends with five separate green tendrils. It is said to monitor the ecosystem, and if the ecosystem falls into disarray, it appears and reveals its power. Zygarde is the only known Pokémon that can learn the move Land's Wrath.

Zygarde 10% is a quadrupedal canine-like Pokemon with razor-sharp teeth and reaches speeds of up to 60mph.

Zygarde 100% is Zygarde at complete power. Zygarde only enters this form if the Core believes it is outmatched.

The Zygarde Core acts as the mind of Zygarde. They communicate through telepathy and monitor the ecosystem.

Zygarde Cells make up Zygarde. They can't use moves and aren't considered to be Pokemon.

Special Abilities
Zygarde has the Aura Break ability, which reverses the effects of Xerneas' and Yveltal's signature abilities. Instead of powering Xerneas' Fairy attacks and Yveltal's Dark attacks, they will be weakened in power.