I am looking for just a few players, to start, and I would be open to working with a co-DM who is knowledgable about the Ravnica world. Players should focus on making iconic builds, rather then just powerful and optimized ones. Your character should be the utter expression of your guild; an Azorius Hussar, who is both a capable justiciar and a capable law-mage; or maybe a skilled Necromancer/Druid summoner, who is tasked with spreading the influence of the Golgari. It's up to you, but it's got to be iconic and focused.
Ravnica is a vast, worldwide cityscape—a patchwork of grand halls, decrepit slums, ancient ruins, and layer upon layer of stonework structures. Of the world's countless civic centers, one looms large above all others: the City of Ravnica, a metropolis so vast that its name has long since become synonymous with the entire plane. It is here, amid mazes of streets and towering gothic spires, that Ravnica's guilds vie for power and control.
Ravnica's guilds had been openly at war for centuries, each claiming dominion over the others. Then something began to happen that gave the guilds pause: The spirits of the dead were lingering in the world. The guild masters of old agreed to divert their energy toward investigating the phenomenon, leading to the signing of the Guildpact, the ancient accord that established relative peace on the plane.
Since that time, Ravnica endured an incredible 10,000 years of peace. Sure, it wasn't perfect, but it was more then enough to foster the city's growth and further it's complexity. Technology flourished and the infrastructure of the city-world grew stronger then ever before. The ten guilds gathered secret armies during this time, however, each of them suspecting that the peace would not last.
They were right. House Dimir, the secretive and hidden guild of Ravnica, hatched a scheme that has been centuries in the making. Labyrinthine plans unfolded and sleeper agents within the other guilds awoke and spread chaos and devastation over the plane. Although the Dimir plans ultimately failed, each of the guilds suffered horrible wounds. For over three years, Ravnica undid centuries of progress, and Ravnica lay in ruins. For awhile, the influence of the ten guilds receded, to the point where some even considered them to no longer be major players in the Ravnican world. Meanwhile, the terrible hauntings that had plagued Ravnica began to vanish.
Smaller guilds began to pop up all over the plane, many of them led by the former members of the more powerful guilds, and mostly occupied by the disenfranchised people of Ravnica. Little did they know that each of the ten great guilds was cherishing an identical moment of respite and recovery. a mere two decades have passed since the Guild Feud, and in that time each of the ten guilds has had only a single purpose. Recruit, Rebuild, and Reconquer Ravnica.
You are one such member. A powerful representative of your guild, you may be a wizened survivor of the Guild Feud, or a young prodigy tasked with rebuilding your guild's influence. In either case, you will travel the wide expanses of Ravnica's many spires and elegant bridges, tasked with the fulfillment of the will of your guild leader.
Each of the ten guilds mastered two of the five colors of mana, and each had its own cultural identity and essential function.
Boros (red-white): The Boros Legion believed in a higher law—one in which righteousness is fire, and justice the light that shines from it. They are the enforcers of Ravnica Law and the only true force standing between Ravnica and total chaos. Led by the powerful war-angel Aurelia, the Boros have spent the past two decades indoctrinating and training new knights and paladins, laying the foundation for the return of the most powerful law-enforcers of Ravnica.
Selesnya (green-white): "Once you are with us, you are an equal among us. Until then, you are lost," said the wolfrider evangel Tolsimir, an agent of the Selesnya Conclave. The Selesnyans believe that nature is the ultimate expression of true Life, and that the spiritual force known as the Worldsoul deserves the prayers and worship of it's citizens. The Conclave suffered harshly in the Guild Feud, and as they began to rebuild they vowed never to be taken as victims again. The Ledev Wolfriders now form the largest portion of the guild, serving the combined roles of evangelizer and guardian - and in some cases, avenger and crusader.
Golgari (black-green): The Golgari Swarm believe you can't truly live until you die. With its vast horde of undead that served as both standing army and labor force, the Golgari operated in Ravnica's undercity, slowly taking over abandoned and derelict areas like a fetid slime mold. Practitioners of druidism and necromancy, the rot-farmers are also responsible for generating the majority of the food for Ravnica. Their insect-riders patrol the undercity, enforcing their own laws away from the gaze of the Azorious. After the Guild Feud, the Golgari drew inwards, and many Ravnicans had to learn to farm and feed themselves - many did not succeed. Now, the guild draws in those who have nothing else to loose, buying their loyalty in exchange for the most basic necessities of life.
Dimir (blue-black): House Dimir was so secretive that only some knew that it even existed. Over the millennia, ghost stories about the Dimir grew more and more complex, telling of ancient, undead necromancer-advisors, phantasmal assassins, and slick, black horrors slithering through the endless maze of sewers under the city. The Dimir were one of the primary causes of the Guild Feud, and many rumours are told that although they lost their guild leader in the fighting, the Dimir suffered the least in the War and are preparing to strike against the world once more. Bodied mostly by mind-numbing psychic assassins and devious spies, the guild may already have it's grips on the world of Ravnica once more.
Orzhov (white-black): To find the Orzhov, the saying went, follow the gold. The so-called Guild of Deals was a rigid hierarchy with the wealthy ghost-patriarchs ruling from the top and countless indentured servants forming the base. Holding this fragile social order in place was a veneer of religious pomp and ritual, though few believed the Orzhov worship any god other than coin. After the fall of the guild in the Feud, the Orzhov returned as a more aggressive and outwardly terrifying group of money-lending religious zealots, and began collecting the massive debts owed to the guild at knife-point. The Orzhov assassins are some of the most skilled on Ravnica, and their faith makes them fearless foes.
Gruul (red-green): The Gruul Clans celebrated base urges and lived by instinct, considering all of civilization to be an elaborate cage that suppresses desire. Once a powerful guild, the Gruul were an assemblage of beggars, gangs, and raiding parties, with the largest of their gangs led by the cyclops Borborygmos. The Guild Feud saw the Gruul Clans momentarily united as mayhem washed over the city. After the fighting began to slow, however, the Clans swept up their war spoils and retreated to their own lands once again.
Izzet (blue-red): The undisputed masters of spellcraft and invention on Ravnica, the Izzet were rabid inventors, fusing elemental magics with technology to power their creations. Led by the capricious and unfathomably brilliant dragon Niv-Mizzet, the Izzet magewrights endlessly created and destroyed, driven only by rabid passion for discovery. During the Guild Feud, the drago-genius and guild Parun fled to some undisclosed location, leaving his guild to fend for itself. Though no one is quite sure why the powerful dragon did not remain during the fighting, the Izzet League survived, battered and bruised, and soon Niv-Mizzet returned and put his servants to work, directing all of their energy to various projects and designs, the outcome of which no one can know, save the draconic wizard himself.
Azorius (white-blue): The Azorius Senate was the primary origin of all laws on Ravnica. The Azorius believed that their rigid system of governance kept nearly everything on Ravnica running smoothly. Justice is blind, and that included the guild's venerable Grand Arbiter, Augustin IV, who some say was blind to Ravnica's most significant problems. During the guild war, elements within the Azorius turned in on itself, causing in-fighting and mayhem within the guild itself. Rumoured to be the doing of the Dimir, many suspect that the entire point was to keep the Azorius distracted, lest they wield their considerable powers against the other guilds and stop the Feud. Now, the law-makers are ruled by the elderly sphinx Isperia, who's brilliance and patience have allowed the Azorius guild to rebuild on a grand scale. Already they have begun to instill martial law on the areas of the plane nearest the guildhall, New Prahv.
Rakdos (black-red): The Cult of Rakdos was a thrill-killing, pleasure-seeking cabal led by the ancient demon Rakdos. Even as a force of chaos, the Rakdos were a resource for the law-abiding guilds; when the denizens of Ravnica needed an obstacle removed or an unsavory client entertained, the minions of Rakdos were happy to oblige. During the Guild Feud, the Cult unleashed their full potential, killing in the streets without discretion and causing more then enough bloodshed and chaos to fuel the Feud. Near the end of the Feud, Rakdos himself was nearly killed and forced into a lengthy slumber. Only a few years ago, the demon unexpectedly returned to Rix Maadi, and began a massive recruiting drive for bolster the ranks of the cultists. His motives are unclear, but everyone knows that Rakdos with an army could never be a good thing.
Simic (green-blue): Amidst the chaos of Ravnican politics and strife, the researchers of the Simic Combine worked industriously to improve their world. The Simic were charged with maintaining nature on Ravnica. In ever stranger ways, the Simic "modified" nature so it could survive on a world increasingly blanketed under civilization. During the Guild Feud, the leader of the Simic, the Elf Momir Vig, unveiled an Ooze Horror called Experiment Kraj, which caused massive amounts of destruction on Ravnica before being re-directed to consume and hopefully destroy the demon Rakdos. Now, the "Science Druids" of the Combine are led by a brilliant merfolk named Prime Speaker Zegana. Her views differ greatly from the radical twisted experiments of Momir Vig, leading the guild down a more sublime, thoughtful and spiritual direction, directing it's members to look inward and seek self-improvement. Through it's innovations and slow but steady progress, the guild has grown incredibly strong in the wake of the Feud, with each of it's members possessing note-worthy power and skills.