Fire Snake (Holiday)

The evening before Hexenstag the people of Altdorf hold a procession called the Fire Snake that passes through the charred and blasted warren of streets around the Bright College, taking in the blackened plaza and splintered ruins around the orders hidden location. At the head of the procession citizens pull a massive metal wagon on which is set a roaring bonfire. And thousands join in behind it, carrying torches and lanterns.

Received wisdom is that the tradition has been going forever, but actually it is a relatively new event, only a couple of hundred years old. It is secretly orchestrated by the College of Fire and is a complex technique for gathering together magnificent quantities of Aqshy in order to power a ritual that is performed over Hexenstag.

Ironically, the boisterous atmosphere of the procession, the ready fire, and the approaching Hexenstag means that the burning of suspected witches and warlocks is quite a common occurrence over the course of the procession.

Source
pg. 12
 * Warhammer Fantasy RPG 3rd ED -- Winds of Magic

pg. 13