"Look at the sky! It is testing us!"
- -Hax Vostillix
Hax Vostillix was the Hall Master of High Cloud in the Knights Academy during the events of The Winter Knights. He both despised and feared Earth-Scholars, believing them to have been responsible for the near destruction of Sanctaphrax in the past. He also believed that Earth-Scholars were responsible for the brutal, unseasonable winter that chilled Sanctaphrax and threatened to break the Anchor Chain, sending the great floating city into Open Sky, and that the only way to save Sanctaphrax would be to purge the city all Earth-Scholars and Earth-Scholar sympathizers.
Hax Vostillix called a massive meeting in the Hall of High Cloud, during the course of which he outlined his plans to once again purge Sanctaphrax of Earth-Studies. He accused the other three Hall Masters, Arboretum Sicklebough, Philius Embertine, and Fenviel Vendix, of Earth-Scholar sympathies, and threw them out of office. He then organized a series of ill-planned Stormchasing voyages to attempt to retrieve Stormphrax from the Twilight Woods, even without evidence of a Great Storm. He also held onto his power by heavily arming the Gatekeepers. Although most academics of Sanctaphrax initially supported Hax's actions, they quickly turned against him when it became apparent that he was only endangering the city further. Unfortunately, with the Gatekeepers armed to the teeth, there was nothing they could do. Even the Professors of Light and Darkness, the two Most High Academes, were powerless to intervene against Hax under the laws of the floating city.
Vilnix Pompolnius assassinated Hax Vostillix, outraged that he had not been chosen for his desired title of Apprentice High Professor. Vilnix planted a bowl of woodwasp egg sacs in Hax's chamber, disguised as delberry bonbons. Hax, miserable as a result of the academics' plummeting support for him, immediately took the candies to be a sign that not everybody hated him. After Hax had eaten one of the disguised woodwasp eggs, it hatched in his stomach, and the woodwasps stung their way out of his body, causing him to die an extremely painful death.