Deino appears alongside another of its species in Double Deino Duo!, when it detects the group's Pokémon eating berries nearby. From there, Silus and Nathan decide to have a competition to see who could catch the Deino first. Deino battled against Nathan's Emolga, but was ultimately defeated and captured by Nathan.
Deino is a small blue skinned quadrupedal Pokémon with black fur covering its head and neck which conceals everything but its mouth from view. The fur around its neck also has six purple spots encircling it, which resemble bruises. The hair on the top of its head takes the shape of a single small horn. It also has a short tail.
Deino is blind, but still is able to battle as a normal Pokémon, as shown in Double Deino Duo!; enough to fend off two Pokémon at once. It possess the ability, Hustle, which increases its Attack power by half, while lowering the accuracy of its physical attacks, such as Headbutt.