Lazav

Lazav is the current guildmaster of House Dimir on Ravnica.

Description
Apart from him being a mindmage and a shapeshifter, details about Lazav are scarce. He (or she, or they ) claims to take orders from some greater power. Lazav has a regal bearing and wears a flowing leather cloak, made from the hide of some beast that had gone extinct ages ago. He is able to warp reality and seems to attract all of the magic in his surroundings toward him.

Lazav's flickering cloak of illusion makes him appear as a blurred, shifting humanoid figure with an ever-changing arrangement of clothes and features. His voice is made harsh and anonymous by a strange buzz, as though heard on the other side of a thick wall.

History
After Szadek was killed and gained control over Agyrem, Lazav managed to gather what was left of the Dimir and bring them together. A ritual was supposed to allow them to commune with the previous guildmaster's spirit, however, it is unknown whether that was true or just a ruse. Since the Dimir guildhall was lost to all, they built a new Duskmantle, which replaced the old structure. Lazav continued to use most of Szadek's methods, giving both their own agents and mercenaries (one of whom is Krenko ) as little information as is required to further their goals.

Lazav suspected that an invader had taken over several guilds, and was actively working against them. He discovered that Bolas represented a direct threat to House Dimir's existence by rendering all its scheming obsolete. Although his greatest wish was to mount a coup and seize power over Ravnica, his greatest fear was that he would have to settle for preventing one.

The shapeshifter cleansed his guild of the agents of Bolas. Afterward, he attended the guild summit where he pledged his guild to the alliance that planned to oppose Bolas.

War of the Spark
During the War of the Spark Lazav assisted Chandra, Saheeli, and Lavinia with shutting off the Immortal Sun. He disguised himself as Chandra in the fight against Dovin Baan, using illusions and an Izzet League flamethrower to replicate the effects of her pyromancy. This deception allowed the real Chandra to sneak into Baan's facility and disable the Immortal Sun, allowing many planeswalkers to leave Ravnica. Lazav subsequently defeated Baan, blinding him with throwing stars made of a strange metal that sliced through Baan's protective spell. Blinded and bleeding, Baan planeswalked away.

Along with the other guildmasters, Lazav participated in a ritual led by Nissa to resurrect Niv-Mizzet and grant him the power of the Living Guildpact. He later also impersonated Saheeli, and survived the War.

Forsaken
After the War of the Spark, Lazav began his plans to subvert the other guilds. He formed a partnership with Teysa Karlov that led to Tomik Vrona becoming the “permanent” acting guildmaster of the Orzhov, allowing Teysa to control the guild indirectly but giving Lazav an opportunity to exploit their leadership. With his secret assassin Atkos Tarr, Lazav had Dovin Baan killed which allowed the shapeshifter to blackmail Vraska. Lazav also partnered with Tezzeret who defeated Ral Zarek and gave up his damaged etherium arm for Ral to show proof of a kill. As a minor setback, Ral had unexpectedly told the truth about his defeat and that Tezzeret lived. Lazav revealed to Tezzeret that he had also infiltrated the Simic.

Trivia

 * His card animation in MTG Arena implies that Lazav may in fact be a dragon in his true form.