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Proof of Ability

Kill 60 Demon Disciples in King's Gorge within 20 minutes, then report to Agritt.
 

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Introduction

Dark Knights only respect the strong. Prove yourself to them by defeating 60 Demon Disciples in 20 minutes. If you can do this, he will tell you the other way to enter the underworld. You should form a party to complete the quest. If you fail to finish the quest in 20 minutes, the rewards will be significantly reduced, but you will be able to continue to the next quest.

NPC Dialog

Dark Knights have no use for the weak. You did
solve a problem that has been plaguing the Tomb
Keepers, so I will give you a chance. If you can
defeat 60 Demon Disciples in 20 minutes in King's
Gorge, I will share with you the second way to enter
the underworld. Prepare yourself for the
knowledge...everything is possible in this world.

Quest Completion

You appear to be powerful enough, you could aid
me...Never mind, I will tell you the second way to
enter the underworld. What you need is the power
of the gods. I told you to be prepared for the
impossible. Even mortals have the chance to obtain
a god's power.