What does a Lunar Ribbon do in PMD2

The Lunar Ribbon is an item used to evolve Eevee into Umbreon and Chingling into Chimeco.

To do so, you must graduate from the guild and unlock Luminous Spring. Place the Lunar Ribbon in your Treasure Bag and feed Gummis to the Pokemon you want to evolve until it reaches four full stars of IQ. Then go to Luminous Spring [the Pokemon does not need to be in your party]. Select its name from the list of Pokemon available to evolve and select the item you want to use to evolve it. If the Pokemon is part of your team, the team will be disbanded, so be cautious.