Saturday, self-styled Superior Sorcerer of the House, stood in her private viewing chamber at the very apex of her dominion, atop the tower that she had been building for almost ten thousand years. This clear crystal-walled room was always at the top, the builders lifting it higher and higher as new levels were slotted in below.

Saturday looked down through the rain-washed glass, at the multitude of fuzzy green spots of light below. It looked like the tower had suffered a vast, vertical infestation of green glow-worms, thousands of feet high, but the spots of light actually came from the green-shaded lamps that sat on every desk in the Upper House, in exactly the same position, just as each desk was set exactly in the middle of an open cube of wrought red iron, with a grille floor and no ceiling.

These cubes -- the basic building blocks of Saturday’s tower -- ran on vertical and horizontal rails, ascending, descending or moving sideways according to the merits of the Denizens who worked at the desks, each hoping to be promoted to the tower itself.

Each cube was dragged into place by a series of chains that were driven by mighty steam engines, deep below the tower. The actual work of building the rails and fuelling the engines was done by bronze automatons and a small number of luckless Denizens who had failed Saturday in some way. Even lower in status were the grease monkeys, Piper’s Children who oiled and maintained the miles and miles of dangerous, fast-moving machinery.

Superior Saturday looked down upon her domain, but the sight of her mighty tower and the tens of thousands of sorcerers within it did not quicken her pulse. Eventually, though she fought against the urge, she stopped looking down and started looking up.

At first she saw only cloud, but then came a glimmer of green light, a darker, more mysterious green than the glow of her lamps. The clouds parted slightly to show the emerald ceiling of the Upper House, which was also the floor of the Incomparable Gardens. Saturday grimaced, an ugly look on her otherwise extraordinarily beautiful face. For ten thousand years she had been building her tower in order to reach and invade the Incomparable Gardens. Yet no matter how high she built, the Gardens moved farther away, and Lord Sunday taunted her by making sure she was the only one to see it. If any of her Denizens looked up, the clouds would close again.

Saturday curled her lip and looked away, but her new view offered no solace. Far off, on the edge of the Upper House, there was a dark vertical shadow that stretched from the ground to the clouds. Close up, it too would shine green, for it was a vast tree, one of the four Drasil trees that supported the Incomparable Gardens above.

The Drasil trees were the reason Saturday could never build her tower high enough, because the trees grew faster than she could build, and lifted the Gardens as they grew.

She had tried to destroy or stunt the Drasils with sorcery, poison and brute force, but none of her schemes had affected the trees in the slightest. She had sent Artful Loungers and Sorcerous Supernumeraries to climb the trunks and infiltrate the domain of Lord Sunday, but they had never farther than halfway up, defeated by the huge defensive insects that lived in tunnels within the bark of the great trees. Even flying was out of the question. High above the clouds, the Drasil’s branches spread everywhere, and the tree’s limbs were predatory, vicious, and very fast.

This had been the situation for millennia, with Saturday building, the Drasils growing, and Sunday remaining aloof and mighty above, secure in the Incomparable Gardens.

But all that had changed with a sneeze on the surface of a distant, dead star. The Architect’s Will had finally been released and had selected a Rightful Heir. Now that Heir was gathering the Keys from the disloyal Trustees. Arthur, his name was — a mortal whose success and speed had surprised not only Saturday.