1 Get the Eon Flute. You get the Eon Flute after completing the Primal Groudon/Kyogre storyline at Sootopolis City. 2 Have three Pokémon in your party with maximum happiness. You can have your Pokémon's happiness level rated from a friendship rater in Verdanturf Town and Pacifidlog Town. 3 Use the Eon Flute to summon Latios/Latias and soar into the sky. 4 Soar to Sootopolis City. Nearby, you'll find a cave called the Nameless Cavern. Land here. 5 Go inside the cave, where you'll find a portal. Interact with the portal to encounter Uxie, Mesprit, or Azelf, depending on the time of day. Uxie appears from 8:00 PM to 9:00 PM, Azelf appears from 9:00 PM to 3:59 AM, and Mesprit appears from 4:00 AM to 7:59 PM