When cracked, they give bonus experience in a skill of the player's choice. The experience given is equivalent to half that of a large fallen star. Only one quest black pearl can be used per day; attempting to use a second pearl gives the message: "You must wait until tomorrow before you can use another black pearl."
Although the pearls grant bonus experience to any player, only members can use bonus experience.
Following the quest, the dead man's chest in the Ashdale Caves can be accessed to fight the final battle against Agoroth again, giving a black pearl with bonus experience in any skill equal to that of a medium fallen star. This can be done once per week, or twice per week for members. Both of the week's pearls may be cracked on the same day. Black pearls obtained after the quest can also be converted to coins.