Izzet League
The Izzet League is one of the ten Guilds of Ravnica. They are responsible for maintaining the civic works of the city: water supplies, sewers, heating, roads and so on. Which is probably not a good idea considering the guild's fickle attention span. Seriously, would you want a guild that needs a giant presumably dangerous spider making buildings its habitat in order for the building to be stable in charge of maintenance? When they're not busy doing this, the magewrights perform magical experiments, often with spectacular (for good or ill) results. This does not really matter to the Izzet, because SCIENCE isn't about "WHY?"! It's about "WHY NOT?"!. Their child-like drive and curiosity, combined with their capriciousness and great intellect, makes them unpredictable at best: they can jump from amicable professor to mad scientist in the blink of an eye.
History
When the Guildpact was ratified the Izzet were given their task of maintaining the civic works. Unlike the other guilds the Izzet have not tried to expand their territory or increase their power: aside from improvements to their fields of expertise their power has stayed more or less the same over the course of millennia. This is in part due to the Izzet not sticking to one idea for too long and in one part due to the fact that the Guildmaster, Niv-Mizzet, finds the thought of running Ravnica too boring. This is much to the relief of the other Guilds, mainly because if Niv-Mizzet wanted to conquer the plane for himself there would be a good chance of him actually succeeding.
Structure
The Izzet League has a rather straightforward hierarchy. At the top sits the Guildmaster, the dragon Niv-Mizzet. His position is a safe one, and all who threaten, annoy or bore him are incinerated by his breath. Below him sit those with access to the Firemind: a link with Niv-Mizzet's consciousness which allows those with the dragon's approval to link with him. This grants those who enter the Firemind access to the Guildmaster's brilliance, greatly enhancing their intellect and allowing them to overcome obstacles encountered during their research. Below this are all the regular members who gather in informal meetings, groups and symposia to study and experiment. The final group consists mainly of goblins who act as servants, test subjects and testers of the Izzet's various spells and devices. High mortality rates are expected, and the Izzet learn what does not work from these tests. But those who are clever and lucky enough can climb the ranks and even gain access to the Firemind, as long as they please Niv-Mizzet.
Guild Members
The vast majority of ranking members amongst the Izzet are humans, while the test subjects are mainly goblins. Less common members include fairies, ogres and human/djinni hybrids.
The guild also employs elementals and creatures called Weirds: elementals consisting of opposing elements. Niv-Mizzet made these to stop the squabbling of various Elementalists, a generous gesture compared to the alternative (setting them on fire).
Finally the Izzet also have drakes that they use as familiars. They also have access to dragons, who might be clones of Niv-Mizzet but intentionally made less intelligent and powerful.
Guild Master
The dragon Niv-Mizzet, the Firemind has ruled over the Izzet since the inception of the guild at the founding of the Guildpact, where he served as one of the ten Paruns who ratified the document. He is extremely intelligent, charismatic, powerful, caprcious, demanding and very, very vain. In this sense he embodies the values of the Izzet (which he named after himself, of course) perfectly: his intelligence and thirst for knowledge combined with his destructive power makes him all the Izzet are in one very large and scaled body. The dragon's relationship with Planeswalkers is unknown: he unwittingly has one in his employ, but he could not Planeswalk himself despite his vast intelligence and it is unknown if he even knew about the other planes at all.
He is also one of the oldest creatures on Ravnica, being at least 15,000 years old. As the millennia went on he appeared less and less in public, eventually retreating into privacy about 7500 years after the founding of the Pact. Just after the Decamillennial, the ten thousandth anniversary of the Guildpact he appeared again to fight against the Nephillim, the Old Gods of Ravnica. They injured him and the Firemind retreated towards the north pole, claiming "he was bored of the fight". After this he was never seen again, and many thought he had vanished for good.
Niv-Mizzet had not vanished for good, however, and after the reinstatement of a new but non-magically empowered Guildpact he signed it on behalf of the Izzet. After his return he began to fervently research the Implicit Maze, and ordered Ral Zarek to investigate the leylines and streets of Ravnica. After his investigations were done Niv-Mizzet announced his findings to the rest of the city and started the run for the Implicit Maze.
Niv-Mizzet appears on two cards, one before and one after the fall of the first Guildpact. He costs 2UURR in both iterations: a 4/4 and a 5/5 with flying. Niv-Mizzet, the Firemind deals 1 damage to a creature or player whenever you draw a card, and you can draw for 1 when you tap him. Niv-Mizzet, Dracogenius has you draw a card whenever it deals damage to a player and can ping a creature or player for 1 when you pay UR. This means that Niv-Mizzet combos with himself, which makes perfect sense given Niv-Mizzet's vanity: ping a player for 1 with the Dracogenius, draw a card, then ping for another 1 with the Firemind.
Guild Champions
Tibor and Lumia are a husband and wife team of wizards: the wise and noble Tibor can grant Flying to a creature whenever you cast a Blue spell while the hot-headed Lumia pings all non-flying creatures for 1 whenever you cast a Red spell. They didn't do anything in the story of Ravnica.
Melek, Izzet Paragon was going to be the Maze Runner for the Izzet but Ral Zarek killed him out of of jealousy and took his place. He lets you play with the top card on your deck revealed, and if it's an instant or a sorcery you can cast it with the added bonus of Twincasting it.
Others
The afore-mentioned Ral Zarek is one of the highest ranking members of the Izzet and reports directly to Niv-Mizzet.
Crix is a female goblin engineer once in the service of the demented magelord Zomaj Hauc. He enhanced her with superior intelligence, speed and flight (by ways of pyromana powered jets in her metal shin bones). She was instrumental in the plan of the magelord to hatch three dragon eggs he found earlier and wanted to use the hatchlings to gain control over the city and defeat Niv-Mizzet. Crix' enhancements proved to be the magelord's downfall when she aligned herself with a group dedicated to defeating him, which netted her a promotion to Master Engineer and access to the Firemind.
Mechanics
As the color of instants and sorceries Izzet League decks employ plenty of sorceries and instants. They are great at removal, either though sheer damage or other tricks. Izzet decks are typically good at whittling down their opponent: pinging a bit alongside damage that is not easily blocked allows for an inevitable victory.
Izzet decks have two weaknesses though: they tend to have a high mana cost while lacking the ability to accelerate their mana. They also don't have particularly good creatures: they are mostly there to improve your spellcasting and perform tricks with their abilities rather than dealing raw damage.
Although thus far the Izzet league has mechanically been associated with instants and sorceries, MaRo has been trying to find a way to make them be an artifacts matter faction, so don't be to surprised if the next time we see them, they focus on artifacts and not instants and sorceries.
Replicate
Replicate is an additional mana cost you can pay any number of times when casting a spell. This copies the effects of the spell and allow it to be given new targets in addition to the first, widening the effect of the spell.
Overload
Overload is a mana cost you can pay instead of the one listed in the top-right. This changes what the spell targets: all instances of the word "target" are replaced with the word "each", effectively targeting every 'legal target' a spell can have (while, for better or worse, by-passing things like heroic, shroud, and hexproof). Some overload cards are similar to non-overload spells. The main difference is that the non-overload spells don't usually specify a player, which in some ways gives the non-overload spells more flexibility. For example, compare Disperse with Cyclonic Rift. You want to save your creature by sending it to your hand and later use it's ETB ability for extra value? Well, Cyclonic Rift can't do that. On the other hand Cyclonic Rift acts either as a Disperse on one of your opponent's permanents, or by paying the overload cost sends pretty much his entire board position back to his hand, causing a huge tempo swing, and flat out eliminating any tokens he had.
Jump-Start
A similar mechanic to Flashback. A card with Jump-Start can be cast from the graveyard as long as you discard a card in addition to paying the normal mana cost.
| Guilds of Ravnica | ||||
|---|---|---|---|---|
  Azorius Senate |
 Orzhov Syndicate |
 House Dimir |
 Izzet League |
 Cult of Rakdos
|
 Golgari Swarm |
 Gruul Clans |
 Boros Legion |
 Selesnya Conclave |
 Simic Combine
|