- "The Siren of the Storm’s tortured soul vengefully roams the world’s seas, singing her paralysing songs of death."
- —Cylostra Direfin.
Legend has it that the sea witch Cylostra Direfin was once the favourite court singer of a Bretonnian king. A fierce lady of considerable size, and temper, she was sent on a voyage across the Great Ocean to sing for the Phoenix King, for the High Elves were known to value arts and music as much as they do gold. The status of her audience wasn't lost on the singer, who dominated the meek captain and ordered his crew around, even having those who angered her flogged. 
But while she was the mistress of the Lamprey, Cylostra could not control the elements. The ship was hit by a fierce storm, blocking the vessel's route. While meek, the captain was still a capable seaman and confronted Direfin at the bow of the ship, where she was watching the storm by herself, insisting that it would be safer to bypass the storm, even if they arrived to her performance in Ulthuan late.
Fuelled by impetuous rage and arrogance, Cylostra Direfin performed a solo mutiny, grabbing the captain by his neck and throwing him overboard, taking command of the ship and crew and making them go through the storm rather than risk being late to her performance. Despite their best efforts, the crew was unable to keep the ship stable. Cylostra, in her mania, stood on the prow and challenged the storm, demanding safe passage if she could sing louder than the winds and sea.
While she sang beautifully, she soon started screaming in fury as she realised she could not beat the storm. Cylostra's arrogant "challenge" ended with her vocal cords ruined, her ship sunk and her crew drowned. As seawater filled her lungs Cylostra, angry at never being able to perform again, cursed the gods and the elements, vowing that death wouldn't stop her and her audience would hear her.
But as she drowned Stromfels, god of storms, sharks and pirates, came to her and made her a deal. He promised her immortality and to be taught sea-magic in exchange for becoming his emissary, the Siren of the Storm.
Decades later, a Bretonnian galleon of rotten wood and tattered sails can be seen navigating the seas even in the most savage of storms. It is the Lamprey, the ship of the vengeful spirit of Madame-Captain Cylostra and her Undead crew, the Drowned. She has sworn vengeance on the Phoenix King, whom she blames for her death, vowing to sink all of Ulthuan so she can finally give her performance to the Phoenix Court.
- Bordeleaux Flabellum - Cylostra wields the ornate ceremonial fan known as the Bordeleaux Flabellum, and can take the field resplendent on the back of a Rotting Leviathan. 
- Lore of the Deep - Cylostra has mastery of the magical Lore of the Deep, dragging those who oppose her to a watery grave that they might finally rise again in her service.
- Cylostra Direfin is an original character created for Total War: Warhammer II with the permission of Games Workshop.