The Master is the nameless writer who gives the book its title: a historian who wrote a novel about Pontius Pilate, saw the book rejected and attacked, burned the manuscript, and ended up in a psychiatric clinic, where he first appears in chapter 13.
He tells Ivan his own story. A historian by training, he worked in a Moscow museum, won one hundred thousand rubles in a lottery ticket, rented two rooms in a basement near the Arbat, and began writing about Pilate. On the street he crossed paths with a woman carrying "abominable flowers, of a disquieting yellow," and the two fell in love at once: "Love arose before us, like a murderer who springs from nowhere in a side street." The editor rejected the novel, the critics attacked it with the term "Pilatism," and the Master, sick with fear, burned the manuscript in the stove.
Margarita rescues him after Satan's ball, and Woland returns the novel to him intact. In chapter 29, Matthew Levi brings Woland the verdict on him: "He did not earn the light, he earned peace." In the end, the Master frees Pilate with a phrase and goes with Margarita to the eternal home.
He enters the book giving up his name and leaves it losing his memory, which begins to fade on the way to the eternal home, right after he finishes his own novel. What remains of him in Moscow is the word with which he bids farewell to Ivan: "Farewell, my disciple."