|The World of Ice & Fire (mentioned)
The pirates of the Basilisk Isles profited from the chaos of the Century of Blood, until seventy-seven years after the Doom of Valyria, when a great plague known as the Red Death swept out of the slave pens and killed nine out of every ten persons, with the rest fleeing. The isles remained totally uninhabited for a full century afterwards, when (during the reign of King Jaehaerys I Targaryen) the Qartheen pirate Xandarro Xhore established himself on the Isle of Toads and the Brotherhood of Bones established themselves on the isles to the west. Ever since, once every generation a major fleet has been sent from the Free Cities to clear out the pirates. Some have ended in failure, but even the successful campaigns seem ultimately futile because new pirates always refill the isles shortly thereafter.
One infamous expedition was led by Saathos Saan. Though he was sent to eliminate the pirates, Saan and his fleet instead turned pirate themselves. He rose to such prominence that he united and reigned the islands as King of the Basilisk Isles for thirty years.