Moonlit market
From Discworld MUD Wiki
The Moonlit Market is a market (duh) that is held atop the Five Ways Bell Tower whenever there is a full moon. The market lasts for three days (Disc Time). Every market the vendors will change, as will their goods. The vendors and wares available are largely assassin-oriented, and include a few items with insignia from the Conlegium Sicariorum houses.