Hyrens are the super-creatures of the Moonlands. If you can obtain one, the rest of the game is a breeze. However, to have one, you must defeat a few...

Naroom | Underneath | Cald
Orothe | Arderial | Core

Naroom Hyrens

On your way through the Underneath Cavern from the Weave, the first branch to the left leads to a stairway down. Use a Blast Urn on the wall to gain access to another corridor. This leads to the Naroom Hyrens' Forest.

Underneath Hyrens

The Underneath Hyrens are found through the Lava Cave. Look for the small "lakes" with stairs going down into them. When the white teleportation mark appears, jump in to appear in the Underneath Hyrens' Cave.

Cald Hyrens

On the Cald World Map, look for the exit in the northwest, and the volcano next to it. Try to walk into one of these volcanoes here. When you enter a room, you will be in the Cald Hyrens' Cave.

Orothe Hyrens

When you have the Orothean Belt, go back to the Seer's House. Jump in the water, and look for a dark patch. You will be sucked in, and you will arrive at the Orothe Hyrens' Cavern.

Arderial Hyrens

Small problem. There is no way to find the Arderial Hyrens without a Gameshark. So go ahead and sulk with the rest of your collection.

Core Hyrens

There is only one Hyren from the Core, and you will find it used by Shadow Magi in the Shadow Hold, in the random encounter scheme of the Arderial Shadow Geyser and the Wastelands, and in the room farthest back from the Core Ringsmith. However, as you need Animite from one of the Thunder Hyren, you won't be able to control one without a Gameshark.