In addition to purchasing Old Reliable, grab all of the. If for one reason or another Dejen is no longer alive, Old Reliable will not be attainable. He is the vendor that will sell Old Reliable to you, which so far is the only known way that you can get this weapon. Go down one level and look for an NPC named Dejen. It will lead to a stairwell that can take you down two additional levels. Once you enter the observatory, turn right and go through another door. This involves following Old Longfellow as he takes you to Acadia.
Assuming you have it, work your way through the main part of the story until you reach Far Harbor and begin a quest called Walk in the Park.
In order to add Old Reliable to your arsenal of weapons, you’ll need the Far Harbor DLC.
