Stolen Knife Quest
Starts on Arrakis. Go to the Living Sietch @ (21, 42) and look around for a mob that seems to be missing a crysknife.(Note: you don't actually have to start the quest with him)
The crysknife you require is located on Giedi Prime, in the area (2n, ne, all n, enter) from the AP. Try searching around.
Once you find the knife, return to the Living Sietch, find your quest mob from earlier and 'say I have the crysknife'