To unlock the Lighthouse’s door at Docks Harbor in Bilgewater, you’ll need to purchase the Lighthouse Key from The Collector, who is a black marks vendor at the Low Tide Market, for 20 black marks. To reach the Low Tide Market, head to the Ship Salvage Yard on the lower level of Docks Harbor near the fishing point. Once you’ve obtained the key, head to the lighthouse and make your way up to the third floor to find a chest. Open it to receive the following:
- 5x Moderate Revival Potion
- 3x Major Group Cleansing Potion
- Silver Bullet
- Purification Ward
- Troll Ring
With Miss Fortune, interact with the telescope across from the chest to receive Tattered Piece of Abigale’s Blueprints.