The Black Pearl is a shop set up by Iskall85 in order to make some profit. It is a hit store that players write down their victim's name in the Black Pearl book, and Iskall will go after them like a hitman. It didn't last long after Grian foiled his plan.
The shop is located under Grian's shipwreck, through a secret underwater entrance. It's made out of mossy stone, cobblestone, and stone bricks. The shop has Iskall85's counter and a chest where the player dispenses a stack of diamonds and writes the player name in the Black Pearl book.
The shop didn't last very long. After Grian pranked an AFK iJevin, he got really mad and spent 64 diamonds and wrote Grian's name in the book. iJevin also told his subscribers to tell Grian he had a hit on his head. Grian didn't blame iJevin and instead prepared for Iskall. He made a safe room with a clever trap that when activated, sends the player into a thin pool of lava, before crashing into bedrock.
Grian was completing his base when Iskall85 came. They had a wild-goose dogfight across the skies before Grian jumping into the safe room, which Iskall85 fell for, leading to his death. After that, Grian bought back Iskall85's stuff and told him 'he was not right for the job'. Iskall85 stopped the store after that.