Enter the Nightmare Domain through Aku in the Land of the Dead, then find Keeper Gabe.

Show Quest Info

Introduction

Aku is impatient, he is very busy with all the souls, but maybe there is something you can help with...

NPC Dialog

You may be a Demigod, but you're still a worthless
mortal. Although...look, there are so many souls
here and I'm very busy. Go to the Nightmare
Domain, someone there will teach you what I need.
You can enter Nightmare Domain by speaking with
Aku.

Quest Completion

You're the first mortal I have seen in a very long
time.