As a Knight Academic in waiting, he was widely known as the greatest of his generation. He was extremely strict on others, as well as himself. In The Winter Knights, he was a staunch supporter of Philius Embertine, and would have interfered in Hax Vostillix’s plans had he not been called upon for a stormchasing voyage. His mission ultimately was a disaster, as his sky ship, the Windcutter, crashed into the Mire before reaching the Twilight Woods.
Screedius Tollinix's desperation to carry out the vows he made to serve Sanctaphrax drove him insane, and he devised a gruesome method to retrieve stormphrax: pose as a guide for those traveling to Undertown, slay them halfway across the Mire, sever their toes, and collect tiny stormphrax particles from beneath their toenails. For 19 years, he built up both an enormous chest of stormphrax and a massive collection of withered, rotten toes.In Stormchaser, he encountered Twig and his crew, and offered them his services as a guide. When they reached the wreckage of the Windcutter, he murdered Spiker and tried to kill Twig, but the Professor of Light, recognizing the remains of the Windcutter, yelled, "Screedius Tollinix!" in despair, under the mistaken assumption that Screedius had been murdered by their guide. Hearing his full name, Screed paused in confusion, and Twig seized the opportunity, stabbing him through the heart. In his last moments, Screed's evil insanity melted away, and he resembled the noble Knight Academic he had once been.