Night of the Black Waltz

During the period in which the Colleges of Magic were being founded in Altdorf, many unexplained events are rumoured to have taken place. In an effort to keep the population calm and prevent them from attempting to lynch the Magisters who now walked among them, these events were covered up. What resulted was a rich tapestry of myths, including many stories of events that almost certainly did not occur. Whether there is truth to stories of entire streets shifting from one side of the city to the other of their own accord, or whether the Docklands really danced a black waltz, will probably never be known for certain.

The story goes that as the fog rose from the river on a night when Morrslieb, the Chaos Moon, was full, many of the citizens of the Docklands took to the streets as one, gliding through a complicated series of occult dance steps, swapping partners and avoiding gawping bystanders with a grace they had never known before. Unable to stop, they danced faster and faster to wild pipes only they could hear, on through the night. Those who tried to stop them or pull them free were ignored or trampled underfoot as the dancers filled the streets until, shortly before sunrise, they collapsed in exhaustion.

From out of the thick pre-dawn fog, Priests of Morr appeared alongside armed men dressed in black. They moved through the crowds in search of those who had died during the night’s events, whether they were stamped to death in the frenetic, swirling dancing or their hearts gave out from the strain. The bodies were pinned to the grounds with stakes, blessed, and decapitated before being taken away on plague carts. They were never seen again.

The official story in the city’s broadsheets was that drunken revelry and rioting had broken out in the Docklands, but the legend of the night of the black waltz persisted. Whatever it was that resulted in the deaths and disappearances that night, it took the heart out of the Altdorf mob at a convenient time.

Source
pg. 5
 * Warhammer Fantasy RPG 2nd ED -- Shades of Empire