Yveltal is a large Pokémon with avian and draconic traits. Its body is dark in coloration and is adorned with grayish patterns along the underside. Yveltal's wings have three spikes on each extending along the bottom edges, close to where they meet the body. There are five large claws on each appendage, three of which curve inwards. Yveltal's underside is bright red, with branching, black markings. Similar markings are present on Yveltal's head and neck.
Yveltal has a pointed, beak-like snout. Black horns extend from above its blue eyes, with a sharply curved portion pointing forward and thinner prongs facing the rear. A feathery gray ruff encircles its neck and billows out over its back. Yveltal has small, birdlike legs with powerful talons. Like the rest of the underside, the legs are red with black adornments, and the talons are gray. Each foot has two toes facing forward and one pointing backwards. When Yveltal's wings and tail are fully extended, Yveltal resembles the Latin alphabet letter Y.
Yveltal has the power to absorb life energy. When it reaches the end of its lifespan, it expands its wings and steals all of the life energy of every living thing around it before transforming into a cocoon to sleep for 1,000 years. Yveltal is the only known Pokémon capable of learning the move Oblivion Wing.