New Phyrexia

Unfortunately for the Multiverse, Phyrexia's obliteration was not complete. A drop of oil found itself in the heart of the golem Karn, himself at the heart of the plane of Mirrodin. This oil multiplied and infected the plane, beginning the slow process of "compleating" it into a new Phyrexia. The people of Mirrodin found themselves at war for the future of their plane. Their efforts were led by three planeswalkers: Koth of the Hammer, Venser, and Elspeth Tirel, each of whom had some previous experience with Phyrexia.

The original, lost Phyrexia was dominated by black mana, a fact reflected in the nature and abilities of its inhabitants. But due to Mirrodin's more balanced nature, the new Phyrexians evolved along each of the five color axes to form distinct factions. Each is led by a Praetor, an uber-Phyrexian general who exemplifies both the character of their color and a different aspect of New Phyrexia. They are:

• Elesh Norn (White), Grand Cenobite of the Machine Orthodoxy and /tg/'s waifu. Norn and her faction represent the religion of Phyrexia.
• Jin-Gitaxias (Blue), Core Augur of the Progress Engine. The faction that follows him is dedicated to perfecting Phyrexia via the path of knowledge.
• Sheoldred (Black), Whispering One, top dog of The Seven Steel Thanes, and also /tg/'s waifu. Her faction is the most similar to old Phyrexia, and operates via open domination and destruction of Phyrexia's enemies (and any Phyrexian who opposes her).
• Urabrask the Hidden (Red), praetor of the Quiet Furnace. Urabrask and his minions oversee the industry of New Phyrexia, including the creation of new weapons and devices. Their connection to red mana (the color of emotion and feeling) led to the most strange and divergent evolution in Phyrexia's history: the beginnings of true empathy and compassion, which led to them refraining from attacking Mirran refugees who initially found their way to Urabrask's domain.
• Vorinclex (Green), Voice of Hunger, praetor of the Vicious Swarm. This faction believes that survival of the fittest is the ultimate law, and that Phyrexians should aspire to be the apex predator of apex predators.

The Mirrans fought bravely with everything they had, and won some battles in spectacular fashion. Elspeth, Koth, and Venser discovered an unusual child named Melira who seemed to be immune to the Phyrexians' infection, and this gave the resistance hope of eventual victory. But in the end, it proved to be insufficient, and the Phyrexians' advantages of time and surprise too overwhelming. The resistance was destroyed, and most Mirrans killed or compleated. Venser died in the process of freeing Karn from Phyrexian corruption, and Koth and Elspeth led the refugees for a time before they were cornered by Sheoldred's forces. Elspeth was able to escape by planeswalking to Theros, but Koth's fate is unclear; all we know is that he promised to fight on regardless. Recent story revelations suggest that the Furnace-based resistance may have been destroyed as well.

If you want to use the phyrexian symbol in text, here it is ϕ. Its a greek symbol called Phi.

Upon its announcement, Magic teased that the fight was still going on as of its development, and that it wasn't certain at the time which side would win. To show this, both "New Phyrexia" and "Mirrodin Pure" were teased as possible expansion names, with Mirrodin presumably becoming purified of the Phyrexian taint should the latter be chosen as the set name. But that didn't happen. Interestingly enough, the name "Mirrodin Pure" is still registered as a trademark, so who knows if a purified Mirrodin might come to pass in the future (Spoiler Alert: Don't count on it for the foreseeable future).

Commander 2015 has revealed a multi-colored Phyrexian, possibly implying New Phyrexia is no longer divided along colored lines (or at the very least, to the same extent it was before). ALL WILL BE ONE!

New Phyrexia was also hinted during the Dominaria storyline to be very much alive, very much active, and is eventually going to be a big deal. In fact, most of Karn's dialogue in the story when he wasn't planning with Liliana and Teferi was him really really wanting to nuke New Phyrexia once and for all before one of them develops a Planeswalker spark.

Update: Toooooooo late! Vorinclex has found his way to Kaldheim, which seems to have something to do with Tezzeret and the Planar Bridge from Kaladesh. While there, he obtained a substance called tyrite, which can be used to convert mortal beings into gods. Jin-Gitaxias would then appear in Kamigawa, investigating the nature of the kami and discovering an artifact called the Reality Chip, which somehow allows Phyrexians to compleat planeswalkers. Urabrask was in New Capenna, looking for help in his ongoing resistance against Elesh Norn, and finding it in the form of Elspeth; you'll notice that he, like the others, needed Tezzeret's help to be there, indicating that our favorite Esperite is still playing both sides. Finally, Sheoldred is in the Dominaria United set, in a ripoff of homage to the classic Invasion block.

Settings of Magic: The Gathering
Pre-revisionist:	First Magic Sets - First Urza Block - Arabian Nights Legends - Homelands - Ice Age - Mirage
Weatherlight Saga:	Portal Starter Sets - Second Urza Block Tempest Block - Masques Block - Invasion Block
Post-Weatherlight:	Otaria Block - Mirrodin - Kamigawa - Ravnica - Time Spiral
After the Mending:	Lorwyn - Alara - Zendikar - New Phyrexia Innistrad - Return to Ravnica - Theros - Tarkir - Eldraine - Ikoria
Two-Block Paradigm:	Kaladesh - Amonkhet - Ixalan
Post Two-Block Paradigm:	Eldraine - Ikoria - Kaldheim - Strixhaven
Never in a standard set:	Fiora (Where the Conspiracy sets take place) - Kylem (Battlebond)

Factions and Praetors in New Phyrexia
	Factions: The Machine Orthodoxy The Progress Engine The Seven Steel Thanes The Quiet Furnace The Vicious Swarm	Praetors: Elesh Norn Jin-Gitaxias Sheoldred Urabrask Vorinclex