The Six Dragons
Solve the monolith's riddle
While Link was busy saving Zora's Domain, Kazul has uncovered a monolith, and needs Link's help to solve the riddle and find the location that it refers to. The inscription on the monolith reads Display the power of the Sage of Water in the presence of the six dragons.
The location in question is in the northwestern corner of Thyphlo Ruins (0185, 3181, 0174). which is a very small peninsula in a mud pit, surrounded by six dragon head statues. While standing in the middle of the peninsula, activate Sidon's ability to create the water shield, then fully charge up and release the water attack (weapon type shouldn't matter, but One-Handers definitely work). This should cause the paved square just past the peninsula to rise from the ground, revealing a chest that contains five Opals.