If the Hero's mercantile is less than 50, Jak only sells potions and lockpicks. The potions include Nightmask potions that are only available from Jak. At higher mercantile levels, he also sells weapons and armor, including enchanted versions.
Also included with the upgrade are many other items in the room below deck where Jak is located, and five chests in the lowermost deck of the Black Flag can be used to store loot.
- He provides training services 24 hours a day but will only buy and sell items from 10am to 11pm.
- He is supposed to wake up at 9am, but because he has nothing to do until 10am he will sleep in for an extra hour.
- His name may be a reference to the pirate Long John Silver in Robert Luis Stevenson's Treasure Island.