Wave Cult Island is an island which has a single cave, the Wave Cult Temple. There also appears to be a mysterious shrine on top of the island, although nothing else is known about the island.
Wave Cult Temple - Warlocks leading a sinister following can be found here, preaching their tidal glory.
Trivia[]
It used to house the Helmet Relic, which was removed in the 1.17 update.
This island was formerly named Kraken Island as there used to be a sign in the temple which said: "Our offering wasn't enough, the kraken will rise once more."