Island Cave

Island Cave is a location in Hoenn. It is located on an island on Route 105 and has two chambers. In the innermost chamber, you fight Regice at Level 40; it will have the moveset Icy Wind, Curse, Superpower, and Ancientpower.

To get to Regice, you must first open the ruins by completing the Braille puzzle on Route 134. This is done by surfing there, diving in the correct place, then travelling to a braille inscription. After reading it, use Dive again to surface in a cave. Go to the north of the room, and use Dig after reading another inscription, and the wall will collapse.

Head into the next chamber and read the inscription at the north wall. Then, put a Relicanth first in your party, and a Wailord last (for Ruby/Sapphire) and read the inscription again. there will be an earthquake, and you should hear the sound of three doors opening far away.

In Emerald, the order is reversed, you put Wailord first in your party, and Relicanth last.

Go back to the Island Cave and enter the ante-chamber. Read the inscription on the north wall, then (for Ruby/Sapphire) stand still and do nothing (do not press any buttons or anything) for about two minutes. Then the door will open, and you can go in to face Regice.

In Emerald, to open the chamber, you must make a clockwise lap of the chamber; sticking close to the walls, after reading the inscription.