Temple of the Ocean King

The Temple of the Ocean King, located on Mercay Island, is a temple dedicated to the Ocean King, and is the primary dungeon in The Legend of Zelda: Phantom Hourglass. It is explored five times throughout the game, each time allowing further exploration. After the first temple is complete, Link obtains the Phantom Hourglass on the first floor, allowing him to spend time in the temple without taking damage. With the exception of the third and the final journey, each of Link's expeditions through the temple are in search of Sea Charts. The only three monsters within the temple are the various Phantoms, the Phantom Eyes, which alert the Phantoms to Link and impede his movement, and Wizzrobes, which steal some of Link's Sand of Hours if they hit him. There are a total of thirteen floors in the temple.

Each time Link exits the temple, the puzzles reset. However, gaining new items also opens up new paths through the temple, allowing Link to find new treasures or shortcuts.

After the player receives the Phantom Sword, the player may participate in a time trial within the dungeon. At the end, they are awarded with two ship parts, the rarity of which determined by how much time is remaining. Because of the many golden pots scattered across the dungeon, which, when broken, give Link more time, as well as the time received after defeating Wizzrobes, it is possible to reach the final room with a net time of 0:00. A guide to achieving this time can be found here.

After the fourth dungeon is cleared, Oshus reveals that he is actually the Ocean King himself. He was sealed by Bellum, but created the alter ego of Oshus. The Ocean King explains that Bellum dwells on the final floor of the temple, absorbing more and more Force.