From the introduction:
The Gloomspires are a collection of towering stone columns that rise from the ocean between the Shackles and Mediogalti Island. For ages, they have remained shrouded in fog that stubbornly resists the strongest winds and magic that causes the columns to shift at random, defying every attempt to count or map them. For Sempet Sevenfingers, a powerful sorcerer and pirate captain at large in the Shackles 300 years ago, the infamous Gloomspires presented the perfect site to hide his ill-gotten wealth. Sevenfingers raided the sea lanes from the Steaming Sea to the Fever Sea in his ship the Voracious, a black-hulled vessel said to have come from Leng itself. As he approached the end of his life, he began renovating the Gloomspire containing his treasure to become his tomb. Key to this transformation was his chief lieutenant Hrethnar, who crafted powerful ritual anchors that he bound into his own flesh to tame the spire’s supernatural nature.