Ravnica is a sprawling cityscape so vast that it covers the entire world. This mosaic of Gothic spires, cobblestone plazas, dangerous slums, and ancient ruins is home to races and cultures of incredible diversity. From the smallest insect crawling through the Undercity to the majestic dragons circling on the horizon, an immeasurable population resides in this metropolis. A traveler could spend a lifetime exploring the open-air markets where anything is for sale, the awe-inspiring cathedrals that dominate the horizon, or the gilded museums showcasing archeological finds from Ravnica's ancient past. All walks of life can be found in this city, and there is a sharp contrast between places like the austere and immaculate Azorius Senate and the chaotic slums of the have-nots. Back-alley deals, crime syndicates, and the black market thrive on Ravnica, but the true power resides with the guilds.
The ten guilds are the foundation of power on Ravnica, each with its own identity and civic function. The guilds have existed for centuries. Their history is a web of wars, intrigue, and political machinations as they have vied for control of the plane. As the wild places of the world vanished under layers of stonework and resources grew scarce, each guild carved out its own sphere of influence. For millennia, the Guildpact, a magical accord, helped maintain a relative peace on the plane. The Guildpact has been dispelled, and for a time the guilds fell into chaos. But the ten-thousand-year-old guild culture and division of duties has reasserted itself, and the ten guilds are once again dominant. However, tensions between them are building and rumors of trouble can be heard in both the hallowed guildhalls and rustic taverns of the unguilded citizens.
The planeswalker Jace Beleren has made Ravnica his adoptive home. But he's not the only planeswalker drawn to this diverse and complex plane. Tezzeret, Garruk Wildspeaker, Liliana Vess, Gideon Jura, and Chandra Nalaar have all visited here, drawn by its secrets and possibilities, and the plane boasts more than one planeswalker native as well.
The average Ravnican is ignorant of the existence of planeswalkers, but some beings on Ravnica are so ancient that they have encountered them personally. Such is the case with the parun and guildmaster of the Izzet League, the dragon Niv-Mizzet. After a years-long absence, the ancient dragon has returned to his aerie and has recently sent his guild into a frenzy of research and projects, which no one seems to understand but him. The League's activities haven't gone unnoticed—that many explosions are hard to miss—and the other guilds are beginning to worry if there is a method behind the Firemind's madness.