In short: Valmiro is sailing away. The quest becomes active after completing Dying of Curiosity and meeting with the Duke.
You can meet him near his house Cassardis. To complete the quest, you need to bring him:
- Potent Greenwarish - can be made of lesser herbs
- Lantern - sold in basic shops
- Sour Ambrosial Meat - there is one slice of meat the Ancient Quarry
- Pilgrim's Charm - sold by Fournival in Gran Soren
Finally, load the chest on the boat.