The Williwaw was a wind spirit who lived in a sea cave in Cape Horn. It often sends sailors to their deaths, creating fierce storms and destroying their ships. Yet, the spirits of these sailors bore the Williwaw no ill will, and protected it and its lair.
The Williwaw whips up fierce storms to destroy ships and kill their sailors. It is incredibly territorial, 'like a vicious bird of prey'. Spending enormous amounts of time building its nest, the Williwaw sinks ships in order to steal their rigging and timber. Its nest lies within a sea cave inside a rock formation in Cape Horn. Half of it is submerged, but the other half, where the creature nested, is dry and contains a broad ledge. The Williwaw would fly in and out through and opening above the waterline.
The creature is described as being, 'a whale washed up on the beach and left to the merciless sun. A broken-winged gull hobbling across the dry sand. A deer collapsing at a dry riverbed.'
The top half of its head is a bird skull, bleached white with a sharp ebony beak. The bottom half was a human, with a wide jaw and a grey bottom lip. Its feet and hands were tipped with talons and bones showed through the dry leathery skin stretched over its humanoid body. Its voice was like the 'vengeful howl of a gale one second, the mad shriek of a hurricane the next. Its wings were black and it wore countless trinkets dangling from golden chains from its neck, one of which was Pyrrha's talisman, given to it by Merrow.
In 1793, Maffeio Aermore, captain of the brigantine Achilles, drove his ship and crew straight for the rocks that sheltered the Williwaw's cave. The spirit, seeing their approach, sank the ship, turning the crew into ghosts. Unbeknowst to them, the captain was secretly the mage, Orfeo who sought Pyrrha's talisman.
The ship's crew remained trapped as ghosts, and protected the Williwaw's lair.
In Rogue Wave, Serafina learns the location of Pyrrha's talisman was in the Williwaw's lair. In Dark Tide, Becca learns about the Williwaw and the Achilles from a bubble tea seller and bribes a cod to swim with her through the Achilles (masking the vibrations she caused while invisible), to steal the talisman. Asking the cod to distract it, the Williwaw snatched the locket containing the talisman off allowing Becca to steal it, but not before it tore a gash through her tail, causing it to fly into a fury, throwing a storm. After escaping the Achilles' crew, Becca is chased by the Williwaw and its storms, untila rogue wave threw her towards the coast.