Eve of Evolution

Eevees
Of all the Pokémon, they are considered the oddest and most versatile specie, able to evolve many different ways into many different elements.
Though, like all Pokémon, they cannot return to their original form.
However, there was one Eevee that made an exception to that rule, and in being such was predestined at birth to embark on the grandest adventure ever begun by any Eevee.
Before, or since...