Decidueye is a tall, avian Pokémon that resembles an owl. The upper portion of its face is dark green with a thin, orange mask-like marking encircling its eyes. Its eyes are reddish-orange and it has a hooked dark green beak. The feathers covering its wings and back are brown, while the rest of its body is primarily white. The three feathers at the tip of each wing are structured similar to fingers and have lighter tips. The backs of its wings and torso are dotted with many white spots, there are six on each wing. The inside of each wing has a line of upside-down, reddish-orange triangles across the top. It has long legs, feet with two toes facing forward and two backward, and short dark green talons. Its tail consists of three long, green leaves.
A leafy hood covers its head and shoulders, and partially covers its face. The hood is smoothly draped across the shoulders and back, but has uneven edges. Around the head, the hood forms many pointed projections that extend over its face. A single white feather with a red base extends from the top of its hood. In the center of its chest is a reddish-orange X shape formed by dead leaves with two thin green vines extending from it. Pulling on the vines closes the hood further over Decidueye's face and improves its focus. The vines can also be used as bowstrings.
While this Pokémon is cool and cautious by nature, it begins to panic if surprised. It can hide from opponents by masking its presence, allowing it to attack unaware foes. It takes only a tenth of a second for it to pluck, aim, and fire an arrow quill from its wings. It is not only quick but also accurate, capable of striking targets over half a mile away.
Hisuian Decidueye[]
Hisuian Decidueye has a smaller wing area and thicker legs. The plumes around its ankles are longer, its feet are black with white talons, and its tail feathers are red. Its head and neck covering are also red, with orange and white accents, and together they resemble an ayaigasa. Its wings appear to have more layers, and the rachises of its feathers are capable of storing air, allowing it to withstand the extreme cold of the Hisui region.
Hisuian Decidueye is said to have a stalwart, fierce personality, although it will tolerate those who do not act hostile towards it. It has a nomadic lifestyle, wandering the Hisui region in search of food. Unlike its Alolan counterpart, it prefers to fight at close range in order to overwhelm enemies. Its legs can deliver powerful kicks that can knock down trees and destroy boulders. Hisuian Decidueye's signature strategy is to fly towards its foes to unleash kicks, then use its hidden arrow quills in order to deliver multiple attacks in a row.
The air stored inside the rachises of Decidueye's feathers insulates the Pokémon against Hisui's extreme cold. This is firm proof that evolution can be influenced by environment.
Decidueye is the only final form of a starter Pokémon that has its secondary type changed upon evolution, with both Alolan and Hisuian Decidueye losing the Flying-type and gaining Ghost and Fighting, respectively.
Of all Pokémon that have received a regional form, Decidueye's regional form was introduced in the shortest time after the species's introduction, being introduced just one generation later.
Hisuian Decidueye is the only regional form that evolves at a different level than its original form.
