Head Priest of the Earth Daichir:
Defeat the monsters that are threatening the safety of this world. I'll tell you which ones to defeat.
First, you must defeat Istina, Octavis, Tauti and Ekimus in an Epic Battle. You must also defeat Beleth and Earth Wyrm Trasken, and bring a Dark Soul Stone.

However, defeating Earth Wyrm Trasken is difficult. That's why I have another method. Would like to hear it?
"Which is it?"
Or you can skip all this and hunt some easier monsters.
"I'll choose this."