From Bulbapedia, the community-driven Pokémon encyclopedia.
(Japanese: 洞窟島 Cave Island) is an island that Ash and his friends visited during their travels on the Decolore Islands.
Prior to the group's arrival, Clair flew on her Dragonite to the island and somehow got separated. By the time the group arrived, Clair was still searching for Dragonite. Alexa temporarily leaves Ash and his friends to find something to film. Ash reunited with Clair and Iris and Cilan meet her for the first time. Ash and Iris volunteer to help Clair search for her Dragonite using Charizard and Dragonite respectively. When Iris's Dragonite found Clair's, he became interested in meeting her but she got into a fight with him when he trampled on some flowers.
On the other side of the island was a cave that was home to a Shiny Druddigon that Clair heard about. Team Rocket also heard about it and use their device to lure it out of the cave. However, this also caused other Pokémon to leave the cave due to the loud noise the device made. With the Druddigon out, it went in a fit of rage and despite Team Rocket's efforts to catch it, Druddigon sent them blasting off. Clair then tried to calm it down and was successful. Druddigon then decided to join Clair's team. Alexa comes back to the group and Clair showed her the Shiny Druddigon that she caught.
Pokémon seen on Cave island