Szadek

Szadek was the parun (founder) of House Dimir, the blue-black aligned guild of Ravnica. The last of an ancient race of psychic vampires, he resided in the shadows for ten millennia in an effort to eventually seize control of the entire city. This plan had him eventually attack the Decamillennial ceremony and, with the aid of his lupul and Savra, he almost destroyed the Guildpact. In the end, he was arrested by Agrus Kos for crimes against the Guildpact, which annulled the guildpact in itself since the pact dictated House Dimir's goal as opposing the Guildpact, making it impossible for Szadek to be legally arrested for crimes against it.

Death and reappearance
Augustin IV, finding Szadek in the Azorius' prisons, killed him and enslaved his ghost. He then sent Szadek to Parhelion to kill the Boros angels and their guildmaster, Razia. Later, Kos threw a grounder containing Szadek's spirit. Szadek broke out of the container and killed Augustin by removing his soul. Szadek plotted to destroy Ravnica using his newfound powers to control the spirits of the dead. It was also revealed that he had taken over the Agyrem district, which had fused with the rest of Ravnica. Kos, now a ghost himself, was appointed as his warden to make sure that he did not escape.

The overlay of Agyrem remained on Ravnica until the Mending, when the Ravnican ghost-world anomaly was dissolved, and the trapped spirits were able to pass on to the aether.

Even after the Agyrem vanished, Lazav, the new guildmaster of House Dimir, claims to have contacted Szadek's spirit and used that knowledge to reestablish the guild.