New Phyrexia (plane)
Factionalizing and the Castes
Unlike in its previous incarnation where Phyrexia fueled itself with colorless artifact mana and the black mana of decay and death, this time the Phyrexians infiltrated all five colors of mana and thus brought war on all fronts. However, this had the unintended consequence of factionalizing the Phyrexians based on their color-alignment. And so each alignment gained a Praetor to oversee that color. They are:
- Elesh Norn, Grand Cenobite – The White Praetor of Unity. Her philosophy falls in line with the ideal of a fascist, unified theocracy. Currently the dominant praetor. 
- Jin-Gitaxias, Core Augur – The Blue Praetor of Experimentation. He leads his faction towards subversive experimentation to understand and exploit their enemies.
- Sheoldred, Whispering One - The Black Praetor of Enslavement. She is the most traditional leader, believing in wholesale slaughter and subjugation.
- Urabrask the Hidden – The Red Praetor of Industry. His philosophy is more industrious than his blue counterpart, building greater and greater artificial monstrosities and weapons. The red mana trait of independence makes this faction the least like the original hive-mind make-up of Phyrexia.
- Vorinclex, Voice of Hunger – The Green Praetor of Predation. He believes most in survival of the fittest and eugenics, killing those deemed weak and augmenting the great predators of Mirrodin.
The Machine Orthodoxy
The white aligned Phyrexians, under the guidance of Elesh Norn, are a very literalist religious organization called "The Machine Orthodoxy". They worship a form of scripture called the Argent Etchings, but divide themselves into smaller sects. Three of the most prominent sects include The Flesh Singularity, The Porcelain Legion, and the Disciples of Karn. They seek to unify the Multiverse as Phyrexia in either a perfect hierarchy or level playing field.
The Flesh Singularity try to achieve total unity by literally flaying the creatures that inhabit the lands and sewing them together. The Porcelain Legion repurpose and adapt creatures by implanting white metal plates into their bodies (considering all white phyrexians have this porcelain like metal on their bodies), while the Disciples of Karn are holding Karn himself hostage and pushing him ever deeper into insanity in hopes of gleaning leadership from his madness.
The Progress Machine
The blue aligned Phyrexians are led by Jin-Gitaxias from the ruined halls of Lumengrid. They hold themselves to higher degree of perfection than the other factions, and pursue what they refer to as "The Great Synthesis". They conduct experiments in various laboratories scattered across the Quicksilver Sea, described as "slaughterhouse like", creating new life forms and technology. They are the most organised group so far, with at least ten observable ranks. One of their great experiments is The Meldweb in which the original Pools of Insight are filled with the brains of hundreds of sentient beings all networked together.
The Seven Steel Thanes
The Black Aligned Phyrexians are out for total and utter corruption, slaughter and enslavement, lead for the moment by Sheoldred. She is at the top of a food chain of thanes, who are all fighting a war of succession to be named the "Father of the Machines". The thanes beside her are:
- Kraynox, the Deep Thane – described as masculine, he lords over the corrupting Phyrexian oil and hopes to construct a fourth layer as a slick, oil-covered vista. Also known as "The Manylegged One".
- Roxith, Thane of Rot – described as masculine, he lords over flesh used as a building and sculpting material, he has plans to design the fifth layer or this New Phyrexian made entirely of flesh.
- Geth, Lord of the Vault – The self-described Thane of Steel, Geth’s undead severed head was offered a deal to give him a necrotechnical body in exchange for his help in the Phyrexian attempt to gain a foothold in Mirrodin's surface. In reward, he was returned his lordship over Ish Sah, the Vault of Whispers.
- Azax-Azog, the Demon Thane - He lords with fear and brutality.
- Thrissik, the Writhing Thane – described as a snake, he fought Roxith. Believes in an everlasting and ever-improving cycle of destruction and resurrection.
- Vraan, Thane of Blood - A compleated vampire who leads a group of vampiric assassins.
The Vicious Swarm
The Green aligned phyrexians were among the first to strike, dominating the Tangle quickly. Like all phyrexians, the members of the Vicious Swarm believe that flesh is weak, but unlike the other phyrexians they believe that New Phyrexia should progress in a more natural way, based on the roles of predation, allowing the strong to emerge triumphant over the weak. They believe that artificial engineering should be restricted to make predators more efficient, and that sentience and sapience are curses, inadequate when compared to the raw power of instinct. Lacking any sort of organisation whatsoever, they are merely a massive variety of creatures that kill each other for the purpose of selecting the strongest.
While Vorinclex is the praetor of this faction, it is Glissa who remains the true power. Depending on what source is more canonical (the field guide or the Quest for Karn novel), she is either loyal to Karn or disdains him.
The Quiet Furnace
The Red-aligned Phyrexians built the Furnace Layer of Mirrodin, based on a similar layer of Old Phyrexia. Their primary function was to tend the forges present there, building weaponry and recycling failed Phyrexians and Mirrans alike. During the war days, they emerged to the surface in the mountains of Mirrodin, and expanded into the surface. While the majority of these Phyrexians still dwell on the depths of the world, several now populate the Oxidda Chain, beasts designed in the fashion of Mirran animals.
Red Phyrexians differ from all others in the way that they have strong emotions and individuality, and as such developed empathy for the Mirrans. While still brutal creatures, their empathy proved strong enough to allow them to let Mirran survivors to dwell on their plane, treating them as if they didn't exist. To hide this secret, as well as to avoid having to deal with other factions, Urabrask demanded that all access to the Furnace Layer be sealed from the other factions, isolating himself and his servitors; the surface Phyrexians in the mountains serve as guardians to the entrances to the Furnace Layer. For the most part, the other factions ignore the Quiet Furnace, with the exception of the Progress Engine, which is paranoid about them.
The Mirran Resistance
The Mirran Resistance are the remnants of the Mirrans that continued to be alive or uninfected even after the compleation of Mirrodin. They are composed mainly of Auriok, Vulshok, goblin, and Leonin survivors together with the last remaining Moriok, Neurok, Sylvok, Elf, Loxodon, and Vedalken inhabitants of the plane. Most of the survivors who are at the later stages of phyresis often die in the camps while they are cared for by those who are less sick, others being the Incorruptable, who are immune to the effects of phyresis. The resistance have no centralised leadership and instead are led by Koth, Venser, Elspeth Tirel, and others in their respective encampments below:
- Bladehold is an Auriok city in the Razor Fields defended by a force known as the Accorders led by Ria Ivor, Hero of Bladehold. Within its reach lies Razor Circle Passages which were created by Ghalma the Shaper in order to help the survivors access the refugee strongholds in the Furnace Layer. The passages are made up of razor grass "crop circles" activated only during the presence of the white sun.
- Lowlight is an encampment formed by surviving leonin abunas led by Kemba situated near the Cave of Light. It is surrounded by enchantments that protect it from the intense heat of the Great Furnace. The camp is made from scraps of skin and geometrically-raised crests of the floor's metal. Squealstokes often raid the camp looking for things to burn.
- Seedling is a camp situated near the Radix. The concept of the name of the camp is based on a story that was told to the camp's leader, Melira, by Thrun about a young tree that grew skyward. Ingot slaves that live near the camp are curious about its existence.
- Slagmaw is the largest camp in the Great Furnace and is also the safest due to its distance from the other lacunae. The camp is located inside a once living creature protecting it from the surrounding environs and, in turn, allowing it to be the best outfitted and protected than the rest.
The Mirran Resistance continue to fight for the eventual purification of Mirrodin. The Sylvok named Melira appears to be the key in achieving their goal. There is also the much-speculated possibility of an eventual Phyrexian civil war, as tensions between and within the Phyrexian factions continue to mount, and the liberation of Karn may very well be the spark needed to ignite it.
Spheres of Mirrodin
According to Phyrexian Field Reports there exists three spheres in Mirrodin: the surface, the interior, and the furnaces. The Phyrexians are currently working on adding spheres to it to presumably recreate the original Phyrexia.