Fly your airship back to the Cave and land on the 2‑tile grass. Once you walk into the Pirates' Hideout, a cutscene occurs and you'll receive the summon Syldra, which is a wind elemental AOE attack.

Leave the cave.
Fly your airship back to the Cave and land on the 2‑tile grass. Once you walk into the Pirates' Hideout, a cutscene occurs and you'll receive the summon Syldra, which is a wind elemental AOE attack.

Leave the cave.