From the introduction:
The pirate Ashur Bael offended the gods of Mount Caz, so they struck his airship, The Void Hatred, from the sky. Thunderbolts tore away the dirigible balloon and slammed the gondola into the cliffs of the holy mountain. Its crew dead, the haunted ship sits on a thin shelf of ice over the bottomless Gorge of Zin. Its engines, fueled by fire elementals, still burn, slowly melting their frozen perch and threatening to explode.
The characters know The Void Hatred still contains treasures worth thousands of gold. They also know about the sword Bael stole from his mother, Jedra the God-Queen of Night, and about the cruel, ever-beating heart in Bael’s chest — a gift from Lursiss, his demon father.