The man who would become The Master is many millennia old, so much so that he can no longer shift into a more human looking form like more vampires have the ability too. Ultimately the Master who has considerable power, becomes enslaved by The Seed of Wonder. During the 1600's the Master began to pose as a cloaked priest, during which time he visited a dying woman, who he would give the name of Darla, Darla would ultimately be his favorite follower in the Order. Around 100 years later he would meet Darla progeny, the vampire called Angelus, who openly mocked The Master for his more demon like appearance laughing in his face, before being beaten by the Master. Darla ultimately chose her life with Angelus, who valued pleasure above The Master and the Order's strict way of underworld life. Seeing Darla's choice, The Master orders his underlings to allow the couple to leave freely, before remarking that he only foresaw their relationship lasting for a century, before it ended.
Ultimately the Master survives throughout the centuries, even battling a slayer by the name of Yuki Makimura, who following the battle sired her. Also during this time, Darla ultimately returned to the Order for good during the early 1900's following her separation with the ensouled Angelus.
By 1937 The Master, came to the New World with the goal of opening the Hellmouth, triggering the end of the world and bringing the return of the Old Ones. Unfortunately for the Master, during his ritual an earthquake struck, swallowing half of Sunnydale, including the church in which The Master was conducting the ritual for opening the Hellmouth. During 1997, the Master's acolytes, began to be dusted by Sunnydale's own Slayer, Buffy Summers. The Master truly began to hate this Slayer following the dusting of his favorite acolyte Darla, at the hands of Angel, almost losing the will to finish his plan, until his most trusted follower The Anointed-One gave him the encouragement to continue.
Following his plan, The Master ultimately is confronted by Buffy in his very own prison, but Buffy quickly succumbs to The Master due to his hypnosis, before being bitten and drowned in a puddle, while The Master escapes the prison he had been trapped in for over 50 years. Fortunately for the Slayer, her friends Angel and Xander had followed her,with Xander giving her CPR, bringing her back from death. Following this Buffy battles The Master again on the roof of Sunnydale High, ultimately dusting him when she knocked him through a sky light, in which he crashed through a table, being impaled by a piece of wood piercing his heart. But The Master, due to his age would leave behind a skeleton, something that ordinary vampires don't do upon there dusting. His order ultimately attempted to use these very bones to bring The Master back from death, before Buffy completely destroyed the bones with a sledgehammer, ending The Master's reign for good.
After Buffy and Angel reject their roles given as the creators of a new universe, and the releasing of thousands of demons from this universe. It is revealed that the Seed of Wonder, which is revealed as the origin of everything . The Seed is revealed to be in Sunnydale, residing in the very church that The Master was trapped in. It's then revealed to the Slayer's that the only way to stop the demon's invasion is to retrieve the seed, which is in the possession of The Master, who is the Seed's protector, and was
returned from death by the Seed's power. Following the battle in the church, Willow gains the Seed, during which time Buffy and a Twilight possessed Angel arrive to the church, during which Angel kills the Master with one blow to the head, dusting him once again.
The Master due to his old age possessed attributes beyond other vampires and even of slayers, having enhance strength,speed, and reflexes in the superhuman range. Also due to The Master's advanced age, he possessed an ability few vampires actually have, the ability of hypnosis, with just the wave of his hand he could draw anyone under his control.