Umbreon is #197 in the Pokedex and is one of possible 7 evolutions that evolves from Eevee when it has gained a complete trust of its trainer at night or when around a Moon Shard. It has a sleek black body with a pair of crimson cat or fox-like eyes and yellow bands on its long, pointed ears and bushy, foxlike tail. Umbreon's forehead and legs have yellow rings on them. Its rings are said to glow at night.
Umbreon can spray a poisonous sweat whenever it gets agitated. As a Dark-type Pokemon, Umbreon can learn several moves with various disruptive effects, such as Taunt or Thief. Despite its appearance, Umbreon is a Pokemon of strong endurance as it has high defensive stats. Since Umbreon is a fully evolved Pokemon, it can learn Hyper Beam and Giga Impact. From Umbreon's Bulbapedia entry
Umbreon also comes in a rare form where its rings shine a blue color instead of the more common yellow. Umbreons this color are vastly rare. I prefer this kind since I love the color blue. :) I always make sure I have a shiny Umbreon on my Pokemon team!