Go to the Soulbound Crypt and gather a Soul Stone from Trapped Devils, then give it to Agritt.

Show Quest Info

Introduction

The souls of the dead make up the gate to the netherworld. You'll need to acquire Soul Stones to pass through it since the Dark Knights have not yet collected enough Soul Stones.

NPC Dialog

I'll never understand why the god of the netherworld
closed the gate. Whatever the reason, it has
become a thorn in our side. It requires a certain
amount of Soul Stones to open, but the demons
sealed in the Soulbound Cave will never give them
to you. We have been able to kill the demons, but
extracting intact Soul Stones from their bodies has
proved to be a challenge for us.

Quest Completion

Tott and I imprisoned the demons in the Soulbound
Crypt. We have been waiting for someone with the
ability to harvest complete Soul Stones from them.
Given your success, It seems you are the one we
have waited for. I greatly appreciate your help.