How do you evolve eevee into umbreon in Pokemon tower defense?

In Pokémon Tower Defense, you can evolve Eevee into Umbreon by leveling up Eevee to level 25 while it is nighttime in the game. Make sure the in-game time is set to night when you reach this level for the evolution to occur. Additionally, ensure that Eevee has high friendship with you, as this is often a requirement in many Pokémon games for certain evolutions.