The law. The Azorius guild is made up of judges, lawkeepers, and officers. The officers go out and prevent crime, with the exception of Rakdos. They are equipped with a radiant whip that ties the offender up and shocks him based on the severity of the crime. Stealing and up is rewarded with death, or given to the Rakdos. The lawkeepers are the leaders of the officers. The judges are there to sentence "evildoers" to either death, life in Azorius prison, or given to the Rakdos (worse by far).
The Guildmaster for the Azorius guild is Esperia, the sphinx. She is the Supreme Judge, and she sometimes judges a case or two in the event of a serious crime (like mass murder, or attempt to murder a Guildmaster).
Sub-guilds are Order and Justice.
The House is the Azorius Tower, where Esperia lives.
The chaos. The Rakdos guild is made up of demons, hellspawn, and torturers. The purpose of this guild is to provide entertainment/punish crimedoers (basically the same thing). The demons are usually the subject of torture. The torturers are... well the torturers. A crime to them is always good... because it means they'll have a new visitor.
The Guildmaster is Rakdos, a giant demon. He never bothers himself with torture, instead, he brawls and/or kills unworthy torturers.
Sub-guilds are Torture and Rage.
The House is the Torture Chamber, near the middle of the city of Esperia.
The science. The Izzet guild is made up of scientists, elementals, and one massive dragon. The Izzet guild is the reason the city is modernized. Without it, there would be no steam engines, no sewer systems, no guns, no weapons of any kind, and no buildings. They use goblin fodder to build all these things, and they construct elementals to test it.
The Guildmaster is Mizzet, a dragon. His motto is "If you aren't doing something interesting, or blowing yourself up trying, you are not worthy of my presence". He leads all experiments, and has done one or two himself. The twist with this guild is that sometimes it does tests... on live buildings. A common phrase on tombs is "Killed by elemental".
Sub-guilds are Experimentation and Technology.
The House is the Izzet Halls, which is two giant towers side-by-side, powering up everything in the city. Mizzet lives at the top.
The swarm. Selesnya accepts any and all as its members. It accepts the handicapped, the wounded, even the dead (as food, of course). It is made up of literally everything. There is no hierarchy. The twist is that once you are a member of the swarm, you are brainswept to accept all ideals of the Selesnya guild. You truly become the swarm.
The Guildmaster is Tel-Merret, a dryad. He believes that everyone is one living organism. He is quite insane, but is as close to "good" as Esperia gets, so they provide a role-model.
Sub-guilds are Peace and Serenity.
There is no House.
The wild. Gruul is made up of ogres, giants, and barbarians. They are anti-civilization. Their Guildmaster does not attend meetings. He takes up fights against buildings. They are barely accepted. They accept all of the crazy, insane people, so they reduce the amount of murders and crime by adding a bit of their own.
The Guildmaster is Borborygmos, a giant. Need I say more?
Sub-Guilds are Chaos and Destruction.
There is no House. They live outside the city.
The dead. Golgari is made up of undead, beetles, and other insects. The dead are thrown into the Undercity, the main base of operations, so they don't need to worry about burying bodies. Golgari is also a good source of information, since it sees almost everything that happens underground.
The Guildmaster is Jared, a lich. Not necessarily evil, he simply things that the best solution to a problem is death, because in death, there is life.
Sub-guilds are Death and Life.
The House is the Undercity, below Esperia, underground.
The intelligence. Dimir is made up of vampires, assassins, and shadowy agents. They collect information, use it to gain money, and assassinate those who would cause trouble to the city as a whole. They are there to remove any who cannot be removed by the law (for instance, Azorius agents and Guildmasters. Surprisingly, Azorius hires them the most.). They actually have Esperia's best interests in mind, as they work to reduce chaos and remove any troublesome figures.
The Guildmaster is Verret-Tu, a vampire. He works for himself and his assassins, a tightly-knit network.
Sub-Guilds are Intelligence and Murder.
There is no House. They are dispersed and meet in secret locations.
The religion. Orzhov is made up of ghouls, priests, and ghosts. They provide the belief, the core feeling, that keeps many of Esperia's citizens going. The twist is that the religion has taxes. Pay those taxes, and you're almost broke. Don't pay those taxes, and your soul is eaten by ghouls, and you become a spirit.
The Guildmaster is the Council of Orzhov, a group of ghosts that actually started the guild in the first place.
Sub-guilds are Extortion and Religion.
The House is the Cathedral, the largest church in the city. There are other, smaller ones.
The creation. Simic is much like the Izzet, except instead of working with inanimate objects like pipes, they work on living things in the eventual goal of making it better. They created merfolk, fish horses, goblins, and other necessary creatures to Esperia. The twist is that they sometimes test on human subjects.
The Guildmaster is Zedra, a merfolk. She oversees all operations and adds ideas of her own.
Sub-guilds are Experimentation and Evolution.
The House is the Simic Growth Chamber Center. It is the main building of operations.
The military. Esperia isn't the only city in this world. Boros is their defense. It is made up of falcons, humans, and Rhox, which are sentient, bipedal rhinos that serve as the commanders. This is the only volunteer guild. Any and everyone can join, it's just that humans are the ones that mostly join. The falcons are giant birds that carry soldiers into battle, and they are bred especially from the Simic. The Rhox live in the Boros Compound.
The Guildmaster is Aurelia, a war-angel. She coordinates all movements. She is present at every battle.
Sub-Guilds are War and Defense.
The House is the Boros Compound, a set of buildings just outside the city. It is where new recruits go, and old recruits live.