Umbreon

Umbreon is a Dark-type Pokémon from Johto region. It evolves from Eevee when fed 25 candies after walking an Eevee Buddy 10 km or more, and evolving it still being Buddy during the nighttime in game.

Trivia

 * There is a continuation of an easter egg that refers to the names of the Eevee Brothers, despite the fact that Tamao wasn't member of Eevee Brother, naming Eevee with her name will result in a Umbreon when it is evolved.
 * Works only once per account and even if Eevee was already evolved into Umbreon not using this method.
 * Along with Espeon and Milotic, Umbreon is one of the only Pokémon in the game that to evolve into them there is other additional requirement than Evolution Item. This requirement is Buddy distance.
 * They do not appear in the wild due to their evolution requirement, as there's Buddy distance required to be walked in order to evolve into them.
 * Works only once per account and even if Eevee was already evolved into Umbreon not using this method.
 * Along with Espeon and Milotic, Umbreon is one of the only Pokémon in the game that to evolve into them there is other additional requirement than Evolution Item. This requirement is Buddy distance.
 * They do not appear in the wild due to their evolution requirement, as there's Buddy distance required to be walked in order to evolve into them.