The Grey King Rules the Iron Islands

In the Age of Heroes, the priests of the Drowned God teach, the Grey King ruled the Iron Islands for a thousand years and seven, until his very hair and beard and eyes turned grey as a winter sea. He wed a mermaid, slew the sea dragon Nagga and roofed his hall with her bones, tricked the Storm God into setting a tree afire to bring the ironborn flame, and taught men to weave nets and sails and carve the first longships. When at last he put aside his driftwood crown and walked into the sea, his hundred sons fell to quarrelling over the isles, and from the sixteen who survived the quarrel the old kings of the ironborn traced their line. The maesters count the tale a fable, yet on Old Wyk the ribs of Nagga's hall stand grey against the sky to this day.