Far to the north, past the cold, vast plains and tangles ancient forests, past even the brooding Deadfire Mountains, lies a real of ice and bitter cold. Barren and stark, few have ventured in to this icy realm. Hunting here is scarce and the wind seems to howl with the voices of demons. Yet there are rumors of a citadel in the heart of the ice field, rising above the wind-swept whiteness and glittering in the pale sunlight. Some say that the citadel was built of block of ice by giants. Others claim that some wild magic caused the structure to grow from the very ice. Yet others state in low voices that it is not ice that shines so, but a fortress of diamonds, built in ages past to guard the most powerful of magics in the world.
In the harbour of a major city a large and terrifying ship made of human nails docks. Nobody seems to inhabit this ominous vessel, someone needs to go on board and unveil the mystery. In comes the PCs.