Any Eevee obtained in Pokémon XD: Gale of Darkness or traded from a Generation III game can evolve into Espeon using the Sun Shard. The Evolution can be cancelled by pressing B or prevented by holding an Everstone, after which the Sun Shard will remain in the player's Bag. In battle, if Eevee levels up then faints afterwards, or the player whites out, the Evolution won't be triggered. If multiple Eevee level up while meeting the Evolution requirements, the first Eevee in the party will evolve; if the Evolution is cancelled for the first Eevee, the next Eevee in the party will evolve instead. The Sun Shard is consumed after one Eevee evolves.
If the save data is altered to add multiple Sun Shards, Eevee that level up in a battle while meeting the Evolution requirements will evolve for as many Sun Shards as there are in the Bag; if there are more Sun Shards than there are Eevee that meet the Evolution criteria, the remaining Sun Shards won't be consumed. If both the Sun Shard and the Moon Shard are in the Bag, Eevee's Evolution into Umbreon will be prioritized over Espeon and any such Moon Shards will be consumed with each Eevee that evolves into Umbreon; if there are no more Moon Shards, any remaining Eevee that meet the Evolution criteria will evolve into Espeon depending on the remaining Sun Shards.
The Sun Shard is the only known way to evolve an Eevee into an Espeon in Orre, due to the lack of time-based events in the games taking place in said region.
Since only a single Sun Shard or Moon Shard is obtainable per game, the player has a single opportunity to evolve Eevee into Espeon or Umbreon (although more of those Pokémon can be traded from other Generation III games) and there is no way to have both Shards in the Bag at the same time.
