Use the Dimensional Gate in Atlantis to reach the Obsidian Turtle Pool. Gather 1 Dim Crystal and 5 Dim Crystal Shards, then take them to Minogame.

Show Quest Info

Introduction

Minogame says that you'll have to confront the Obsidian Turtle directly in order to find out what's going on. The Dim Crystals are crucial to the Obsidian Turtle's plans, so Minogame has asked you to steal them to buy some time.

NPC Dialog

The only way we'll ever figure out what's going on with the Obsidian Turtle is by confronting him directly. You've seen the Dim Crystals around here, right? Yeah, those are important.
Those crystals convert the dark energy here into a form that the Obsidian Turtle can use. Snatch them and bring them here; if that doesn't get his attention, it should at least buy us some time. Watch out, though; one of them was so overloaded with dark energy that it burst. You'll have to find the pieces.

Quest Completion

It will take some time for the Obsidian Turtle to replace the destroyed crystals. Now's our chance!