Dappa is a member of The Cabal and an adept linguist and writer. He was raised in what is today Nigeria, in a village that profited from the slave trade. In time, he came to realize the evils of the trade and attempted to change the way in which the elders of his village prospered.
For his trouble, he was enslaved himself, and found himself eventually passed along to the Barbary Corsairs. There, he befriended Jack Shaftoe and the other members of the Cabal and shared their adventures in their years-long journey eastward around the world. Dappa comes to serve as the executive officer of Minerva; he and the ship's captain, Otto van Hoek, form a strong and effective team.
Dappa comes to dedicate his life to ending slavery. In his travels, he goes out of his way to record and published the tales of slaves in an attempt to raise public awareness of the evils being perpetrated on so many. He eventually befriends Eliza, who becomes his patron in this work.
When in London in 1714, he is falsely imprisoned by the sadistic Jacobite Charles White, who claimed that Dappa was his escaped slave and offered a hefty reward for his return. While held in the Clink, Dappa uses his status to become a tabloid celebrity, and is freed after fighting a most unusual duel, using a type small of cannon called a hobit or haubitz (an early form of howitzer), on the lawn of the Tower of London. Immediately following the duel, he flees London aboard Minerva. His fate after this is not known.