Most Stygian wraiths know Gorool as the Godzilla-like Neverborn Malfean that threatened the city of Stygia in the closing days of the Fifth Great Maelstrom. Charon, in his last act in the Underworld, challenged Gorool in the Weeping Bay and fought him to a standstill before both disappeared in a whirlpool.
What is known only to a few is that Gorool was possessed of the knowledge and animating force of Charon's Shadow.
Sister Acceptance and some other senior Pardoners know part of the tale: by the early twentieth century, Charon's Shadow was running amok. Even in the periods when Charon was free of Catharsis, he was inevitably going mad. In order to prevent further damage to his sanity and Stygia, Charon submitted himself to a powerful and experimental Castigation. The end result was that his Shadow fled his Corpus and took on a form of its own, somewhat like the Ritual of Severance of the Ferrymen.
What happened next is known only within the depths of the Labyrinth. Charon's Shadow came there, in time, and wandered its lengths until it stumbled into Gorool's lair. The Neverborn devoured the Shadow, absorbing its knowledge as he stripped out its consciousness, and set that knowledge to use when he rose against Stygia.