In a flashback in Team Eevee and the Pokémon Rescue Squad!
This Umbreon is a Dark-type Pokémon owned by Virgil.
When Virgil was going through a journey, Eevee was his first Pokémon in his possession before evolving. Virgil and Eevee were lost in a forest, during the night and as it seemed all hope was lost, Eevee evolved into an Umbreon. Using Flash to glow in the dark, Umbreon helped Virgil navigate through the forest by using its glowing rings.
When the heroes arrived to Virgil's house, Virgil sent his Pokémon, including Umbreon, who was a part of his team. Umbreon used Psychic to help create a key to unlock a locked door. Inside the dam, Umbreon used Flash to illuminate the area. During the battle with Cryogonal, Umbreon used Shadow Ball, and along with Glaceon's Ice Beam, Cryogonal's Light Screen was shattered.
Umbreon helped Virgil to calm down a wild Garbodor and a group of Trubbish, countering their Gunk Shot with Shadow Ball. Umbreon defeated Flora's Gothitelle in the fourth round of the Vertress Conference allowing Virgil to progress to the Top 8. It was also used off-screen in Virgil's Vertress Conference battles against Cameron and Dino.