Irida has found a treasure and challenges you to a battle to get it.
The Request
Talk to Irida at the Pearl Settlement in Alabaster Icelands to accept this request.
Battle Irida
You will battle Irida's level 64 Glaceon, level 32 Espeon, and level 32 Flareon, all at the same time.
Reward
After you win, you get the Lustrous Globe, which can be used with Palkia. You also get 3 Comet Shards.