A One-Round Living Greyhawk Principality of Ulek Regional Adventure
From the introduction:
With derro poison antidote supplies dwindling and sightings of derro near the village of Thrutch, you are asked to delve into unknown underground tunnels in search of a key ingredient. Can you successfully complete this mission without upsetting the balance down below?
A Principality of Ulek regional adventure for APLs 4-12.