Master of the House
The Master of the House was the Master of the Strange and Wonderful House. There were multiple Masters over the House's history.
Nature
One elder Maid was openly dismissive of the claims of those who saw themselves as “rulers” of the House; in her view, the House ruled itself, and all the members of Staff, Master included, were but custodians. As such, among the Maids' duties was “watch the House while the Master is away”. (PROSE: Our Strange and Wonderful House: The Maids)
The modern-era Master believed himself to be one of the writers who had “made” the House, although Sid believed this whole way of looking at the nature of the House to be incorrect, or at least limiting. (PROSE: Our Strange and Wonderful House: The Secrets of Our Gardens (Part 2: Acccursed Springs)) A man who had been part of the group who had “dreamed up” the House would later believe that he was its last survivor. (PROSE: Our Strange and Wonderful House: Remnants and Reminders) This Master had “memories the size of a million eternally propagating multiverses”, describing himself as being “on the infinity kick” when he occupied his function as Lord of the Manor. (PROSE: Our Strange and Wonderful House: The Will of the Creator)
The Master of the House resided in the Master Bedroom, and was the only one allowed into the Stationery Room except for people to whom he explicitly granted permission. (PROSE: Our Strange and Wonderful House: The Stationery Room)
Interestingly, there also existed a Master of the Fields, the symbolic leader of the people of the rural towns surrounding the Strange and Wonderful House in its native universe. It was this Master's responsibility to lead the Harvest Procession that brought victuals to the House for the winter through the Great South Gate every year on Harvest Day, riding on the lead cart, which was pulled by a team of eight, unblemished black oxen adorned with ribbons. (PROSE: Our Strange and Wonderful House: The Great South Gate)
History
Victorian era
A century before the “coming of the elevator”, the Master of the House “at that time” kept a mistress. After a parlour maid discovered the true nature of the Airing Cupboard, he installed a life-sized portrait of her over the door. This outraged the Master of the House's wife, and it was later said that she instantly moved back to the continent, where she died of jealously soon after. (PROSE: Our Strange and Wonderful House: The Airing Cupboard)
Modern era
A century later, when the disturbances caused by the Elevator's appearance caused the door to the Cupboard to be rediscovered, a visitor would enter the Cupboard only to be confronted by a ghostly figure in a Victorian nightdress who referred to him as “darling”, told him off for having been “ages”, and pulled him into a deadly hug. (PROSE: Our Strange and Wonderful House: The Airing Cupboard) By this point, the new Master of the House also had to carry out negotiations with the Goblin King, requesting from Montresor that a special bottle of memory-wine be brought up from the Cellar to make them go more easily, (PROSE: Our Strange and Wonderful House: The Cellar) after the Goblins of the House became upset about the project of installing an Elevator in the House to bypass the Stairwell. (PROSE: Our Strange and Wonderful House: Elevator)
In a bad mood after an argument, the Master of the House (PROSE: Our Strange and Wonderful House: The Will of the Creator) stomped out of the House proper through the Sun Room. Ignoring the signs pointing to the Tree House and the Southern Veranda, he made his way to the Gardens, where a sign warning visitors to be careful of the Werepanda only needled him further. After entering, he was confronted by a strange man (PROSE: Our Strange and Wonderful House: Into the Gardens (Part 1)) who offered to take him on a tour of the Gardens, enticing him to accept with the possibility of “tea in the shade of the Bodhi Tree” at the end of the tour. (PROSE: Our Strange and Wonderful House: Into the Gardens (Part 2))
The old man, Sid, walked quickly, chattering happily to his charge about what they saw on the way and what else they might see yet, from the orchards and vegetable garden to the Topiary Veranda and we I. T. Haze's hedge maze. (PROSE: Our Strange and Wonderful House: The Secrets of Our Gardens (Part 1)) When Sid showed his charge “the training ground of accursed springs”, the latter expressed surprise at such a seemingly malevolent thing being part of House. Sid tutted at his “mistaken impression that the House is essentially good” before adding that “even worse, like many new writers, you think you’re in control of every part of the story”; when the visitor replied that “we” did in fact “make” the House, Sid cryptically implied that this was a limited perspective. They continued walking and found themselves in a landscape which the visitor believed to be “in China, or Japan”, to which Sid replied that “all three are correct, depending on your perspective”. The visitor suddenly felt calmer and realised that in the distance, he could now glimpse the towering form of the Bodhi Tree. (PROSE: Our Strange and Wonderful House: The Secrets of Our Gardens (Part 2: Acccursed Springs))
Sid left him to take the last few steps alone. Though briefly suspicious, he was won over by the aura of peace that surrounded the Tree, and agreed, kicking off his shoes to finish the journey alone. (PROSE: Our Strange and Wonderful House: A Return to Innocence) As he approached the Tree, he was overcome with a surge of emotion and cried out all his buried feelings of “unworthiness, self-hate and guilt”. When had no further tears to shed, feeling a new man, he asked if it was “always like that”, but found Sid out of earshot. He felt at peace and increasingly certain that he feels not just good, but great — “fully rested, at peace, and ready for anything”: ready to “change the world”. (PROSE: Our Strange and Wonderful House: The Pain of Rebirth) He paused at last to consider the huge, beautiful Tree itself, and reached out to brush a hand against its barks; as he did so, he felt the Tree's ageless mind briefly touching his own, getting a glimpse of the Tree's timeless perspective on the universe. (PROSE: Our Strange and Wonderful House: The Bodhi Tree)
Finding Sid again, he was given the choice of whether to stay by the Bodhi Tree's side indefinitely, or to return to his normal life, at the cost of the humdrum complications of everyday life slowly chipping away at his enlightenment until he'd all but forget what he had really found here. He found the choice unfair, (PROSE: Our Strange and Wonderful House: Wake to Dream Again) and, an incalculably amounts of times over, returned to the Tree before seeking Sid out again, being offered the choice again without remembering it was not for the first time, and again returning to the Tree. At last, he realised how many times he had repeated the pattern, and, complimenting Sid's patience, said he was ready to return. Sid reminded him of his true identity by telling him that “the Manor await[ed] its Lord”, and his memories and lust for life came crashing back into his mind like a storm. Grinning, he headed home from his “vacation”, once again on “the infinity kick”. (PROSE: Our Strange and Wonderful House: The Will of the Creator)
The unkempt inspector who spent their career travelling through the House examining each of the hundreds of Airing Cupboards once reflected that there would be “hell from above” if it became known that they had no means of making sure they didn't visit the same Cupboard twice, meaning that their task might literally never be finished and their count might be faulty. (PROSE: Our Strange and Wonderful House: The Seven Hundred Nineteenth Airing Cupboard)
Behind the scenes
Before the reveal in Zxvasdf's The Will of the Creator that he was the Master of the House, Robert Quick seems to have written the first-person narrator of the “Garden” storyline as an in-universe version of himself.