Hidden below the streets and towering buildings of Ravnica, there lies a vast subterranean environment known as the Undercity, or Old Rav. As sprawling and varied as the city above, the Undercity is made up of sluiceways, sewers, huge vaults, fungal forests and caverns both natural and artificial. Whole neighborhoods and districts reside here, in buildings and structures that once took in daylight in Ravnica’s ancient past before the march of progress had the city grow higher and higher, leaving these areas in the dark. Many who live here have never seen sun before, and have adapted to life in the shadows.
It is not difficult to access the Undercity from the surface, as all one needs to do is find a way down. All manner of tunnels, crevasses and canyons connect and bisect the Undercity, and in some places magical lifts exist that allow for quick access to even the deepest reaches. Whether or not one actually wants to travel there, though, is the real debate – the Undercity is not a place for the unwary or unprepared. At best, it is a shady place, teeming with those businesses and people that the surface folk would normally find unsavory – black markets, brothels, and the slave trade exist among more legitimate businesses, many of whom actually try to put in a honest day’s work; at worst, the Undercity is perilous, a nightmare of fetid tunnels that breed disease, brackish lakes that hide dangerous creatures, and places of utter darkness where one can easily be set upon. Some of the blacker, deeper reaches hide unknown horrors, things the average citizen would rather be left forgotten.
Among the guilds, several have major footholds in the Undercity. The Golgari Swarm are the most apparent power of the bunch, as they operate and base themselves almost entirely in the underground. As most of Ravnica’s refuse eventually end up in the Undercity, the Golgari work actively to turn trash into treasure, their food production and growth fueled by numerous rot farms, corpsefloat valves and fungal insect hatcheries. Another prominent but less-widespread guild is the Cult of Rakdos, able to practice their carnal rituals and add to their numbers away from the eyes of the Azorius and Boros. Rakdos cabaret theaters, revues and nightclubs can be found in many places here, combining entertainment and depravity in all manner of creative and disturbing ways. House Dimir is less seen but never doubted as frequent dwellers of the Undercity, and rumor has it their primary headquarters lie somewhere in the most secret, gloomy corners of Old Rav. The Orzhov Syndicate have a more clandestine presence, as most of the hierarchy prefer to stay close to their gilded surface mansions but have agents, enforcers and mages in Old Rav, and some Orzhov vaults and tombs extend quite deeply into the Undercity.
Of late, the Izzet League have shown an unusual interest in certain parts of the Undercity, which had lead to frequent clashes with the Golgari over territory.