Use Obsidian Turtle Seal anywhere in Obsidian Turtle Pool to summon the Obsidian Turtle. Defeat it, then return to Minogame .

Show Quest Info

Introduction

Just like Minogame said, the Obsidian Turtle appeared after you approached the Dim Crystal. It is by far the strongest of the Four Guardians, but capturing it may be the only way to find out the truth.

NPC Dialog

The Obsidian Turtle has shown himself. Do what
you must, but be warned that he is not a foe to take
lightly. I doubt you will be able to take him alone.
Use this Obsidian Turtle Seal to call him forth, but
do not do so unless you are confident that you are
fully prepared.

Quest Completion

You have captured the Obsidian Turtle. Are you
satisfied now? Do you still believe there is some
conspiracy? Your business here is over, so you
should...

Wait! What's that!?