Quest 64/Quest for the Water Jewel

Larapool
After defeating Zelse in the Windward Forest, bring the Wind Jade back to Leila in Larapool, and she'll open the door under the fountain. There, the magic of the water is released, and you can get three more spirits and access the Blue Cave.

Chest items:
 * Silver amulet

Blue Cave
Monsters of the Blue Cave:

Chests in the blue cave:
 * Heroes drink
 * Healing Potion
 * Mint leaves
 * Healing potion

There are six spirits in the Blue Cave.

The blue cave can be subdivided into three parts.

In the first part, you'll meet a series of forks. Blue stones with a sign will tell you which way to go, but if you take the other direction you'll find one or two items at the dead end. If you end in a dead end anyway, it just means you missed a fork: just backtrack, and change route.

The second part is dominated by a large dome free of monsters: take the opportunity to replenish your magic points and heal a bit. A U-shaped bridge will bring you to another tunnel, but you'll end up on a second bridge that crosses the dome.

The third part is a maze on a subterranean lake. The shortest (and simplest) way through is as follows: at the first fork, take the central path, then always take the left one, until you get to the exit. The monsters here are quite weak, as they are from Cull Hazard cave, but they'll attack mostly at the crossroads trying to break your orientation. If you explore this cave you'll find some spirits and chests. At the end of the maze, a tunnel brings you to the Crystal Valley.

Crystal Valley
People of the Crystal Valley:
 * Epona
 * Chappy at Epona's Cottage lets you save game

There is one spirit in the Crystal Valley.

Talk to Epona, and she'll let you use a magic circle in her cottage to get straight to the Isle of Skye.

Seagoing ship and isle of Skye
Monsters of the isle of Skye:

People of the isle of Skye:
 * Kiliac
 * Boren on the Seagoing Ship lets you save game
 * Macren
 * Colleen

Chest on the isle of Skye:
 * Dragon potion

There is one spirit on the pirate ship and four more on the isle of Skye.

Although the island is small, the monsters are abundant. Talk to Colleen in the cottage, then walk to the top of the island. There, a magic circle will teleport you to the bottom of the lake, where you can meet Nepty.

Nepty
The name of Nepty is a reference to Neptune, the Roman god of the sea.

After retrieving the Water Jewel
You can now walk back to Colleen cottage, and the door inside will open revealing a magic circle that teleports you back to the Crystal Valley. There, Epona will activate another magic circle that teleports you back to Larapool.

If you go back to Dondoran castle (use some wings to make it faster), go to the library upstairs. The power of the Water Jewel activates a secret passage, and you can get an extra spirit.