Blackscrip is the in game quest currency to buy prizes from the shanty, similar to tickets at Chuck-E-Cheese. Blackscrip granted at the end of a quest are based on performance in the quest. They are also tied to the character. In order to accumulate Blackscrip from multiple runs of a quest, the same character must go on the quest. The only current way to earn Blackscrip is to participate in Troubled Waters, Rescue at Sea, which costs $9.99 per two hour run. The maximum achievable Blackscrip per run is 150.
The amount of Blackscrip earned by a character can be checked using the TICKET verb.