Mutator

The mutator is a multicolored evolutionary stone owned by Vergil. It may be unique, as no other has been seen in the series. It was brought from a very far region by Ash Ketchum.

The mutator allows the trainer's eevee to evolve into any of its evolutions temporarily. To do so, it must first absorb the power of an evolutionary stone for water, fire and electric type eeveelution, for espeon it needs sun shard and high friendship, and for umbreon a moon shard. Intially the mutator has one color with many segments, but when a stone or shard is absorbed, the corresponding segment will be colored with the respective color. After that, the corresponding eeveelution will will be permanently available to the trainer.

Vergil acquires a water stone from his mother's gym and unwillingly absorbs the water stone into the mutator. Eevee then evolves into vaporeon. Then, he acquires a moon shard inside viridian forest, again unwillingly, when a gengar tries to attack him while holding it. This causes eevee to evolve into Umbreon.