The rustle of paper was what Dalia imagined the ocean to sound like, the clatter of adding machines and the rattle of brass keys on the typesetters like the motion of uncounted pebbles on a beach. Of course, Dalia had never seen the things she imagined, for the seas of Terra had long since boiled away in forgotten wars, but the words she read as she copied text from the reams of paper and armfuls of data-slates carried in daily by muscled servitors had filled her mind with possibilities of worlds and ideas that existed far beyond the confines of Terra's mightiest scriptorium.

Emerging from the musty darkness of the Librarium Technologica, she had been blinded by the brightness of the day, the sky a brilliant white and the sun a hazy orb peeking through scraps of clouds the colour of corrosion.

The air was cold and thin at this altitude. She could just make out the tips of the slate-coloured mountains that crowned the world over the teeming roofs and spires crammed together in this part of the Imperial Palace. She had longed to see the mountains in all their glory, but her escorts marched her through dark streets that sweated steam and oil and voices towards an unknown destination without pause.

That destination turned out to be a landing platform, upon which sat a vapour-wreathed starship, its hull still warm and groaning from the stresses of an atmospheric entry.

She was led into the cavernous hold and deposited on the floor while the Protectors took up their allocated positions and the mag-locks secured them to the deck. With a juddering roar and sudden lurch, the starship lifted off, and Dalia was thrown to her knees by the violence of the ascent. Fear gripped her and she clung to a protruding stanchion as the angle of incline increased sharply.

The thought that she was leaving the planet of her birth struck her forcefully, and she experienced terrible panic at the thought of venturing beyond her known horizons. No sooner had she chided herself for such timidity, than the panic subsided and she felt her stomach cramp as she realised how hungry she was.

The roaring of the starship and the vibrations on its hull grew louder and more violent until she was sure the craft was going to tear itself apart. Eventually, the noise changed in tone and the starship began to level out, powering through the void at unimaginable speeds.

She was travelling on a starship.

With a moment free to think, she now wondered where she was going and why the Mechanicum Protectors had plucked her from the Librarium's cells and for what purpose. Curiously, she felt no fear of this strange voyage, but she attributed that lack to the mystery and interest of it being enough to overshadow any wariness she felt.

Over the next day or so, her escorts - she did not now think of them as captors - resisted her every attempt at communication, save to instruct her to eat and drink, which she did ravenously, despite the food's chemical artificiality.

They did not move from their locked positions at all during the journey, standing as mute guardians and offering her no diversion save in the study of their forms.

Each one was tall and powerfully built, their physiques gene-bulked and augmented with implanted weaponry. Ribbed cables and coloured wires threaded their robes and penetrated their flesh through raw-looking plugs embedded in their skin. She had seen Protectors before, but she had never been so close to one.

They smelled unpleasantly of rotten meat, machine oil and stale sweat.

They were armed with giant pistols with flaring barrels, and tall staves of iron, topped with a bronze and silver cog, from which hung a scrap of parchment that fluttered in the gusting air within the cold compartment.

A set of numbers was written on the parchment, arranged in a four by four grid, and Dalia quickly worked out that each line added up to the same number, no matter which way they were combined - vertically, horizontally or diagonally. Not only that, but each of the quadrants, the four centre squares, the corner squares and many other combinations added up to the same figure.

'Thirty-four,' she said. 'It's always thirty-four.'

The design was familiar to her and Dalia knew she had seen it before. No sooner had she wondered where, than the answer came to her.

'The Melancholia,' said Dalia, nodding at the parchment.

'What did you say?' asked the Protector.

His voice was human, but echoed with a metallic rasp beneath his bronze mask, and Dalia was momentarily taken aback that he'd actually responded to something she said.

'The symbol on your parchment,' she said. 'It's from an engraving. I saw it in a book I transcribed two years ago.'

'Two years ago? And you still remember it?'

'Yes,' nodded Dalia, hesitantly. 'I kind of remember stuff I've read and don't forget it.'

'It is the symbol of our master,' said the Protector.

'It's from an engraving of one of the old master prints,' said Dalia, her eyes taking on a glazed look as she spoke, talking more to herself than the Protector. 'It was so old, but then everything we transcribe in the great hall that's not from the expedition fleets is old. It was a picture of a woman, but she looked frustrated, as if she was annoyed at not being able to invent something ingenious. She had all sorts of equipment around her, weights, an hourglass and a hammer, but she looked sad, as if she just couldn't get the idea to take shape.'

The Protectors glanced at one another as Dalia spoke, each one gripping his stave tightly. Dalia caught the look and her words trailed off.

'What?' she asked.

The Protector disengaged the mag-lock clamps securing him to the deck and stepped towards her. The suddenness of his motion took her by surprise and she stumbled backwards, falling onto her backside as he loomed over her, the green glow of his eyes shining brightly within his tattered hood.

'I begin to see why we were sent to fetch you,' said the Protector.

'You do?' asked Dalia. 'And you were sent for me? Me? Dalia Cythera?'

'Yes, Dalia Cythera. Rho-mu 31 was sent to fetch you from Terra.'

'Rho-mu 31?'

'That is our designation,' said the Protector.

'What, all of you?'

'All of us, each of us. It is all the same.'

'All right, but why were you sent to fetch me?' asked Dalia.

'We were sent to fetch you before you were executed.'

'Executed?' exclaimed Dalia. 'For what?'

'Magos Ludd invoked the Law of the Divine Complexity,' explained Rho-mu 31. 'Individuals so accused attract the attention of our master.'

Dalia thought for a moment, her eyes fluttering beneath their lids as she recalled what that law concerned. 'Let me think, that's the belief that the structure and working of each machine has been set down by the Omnissiah and is therefore divine… and that to alter it is, oh…'

'You see now why we came for you?'

'Not really,' admitted Dalia. 'Anyway, who is your master, and what does he want with me? I'm just a transcriber of remembrance. I'm nobody.'

Rho-mu 31 shook his head, making a fist and placing it over the silver and bronze cog atop his staff.

'You are more than you realise, Dalia Cythera,' he said, 'but that, and more, will become clear to you when you meet our master: High Adept Koriel Zeth, Mistress of the Magma City.'

'The Magma City?' asked Dalia. 'Where is that?'

'At the edge of the Daedalia Planum, on the southern flank of Arsia Mons,' said Rho-mu 31, lifting his stave and touching it to an opaque panel on the vibrating hull of the starship. A flickering light crackled, and the panel began to change, slowly becoming more and more translucent until finally it was virtually transparent.

When this transformation was complete, Dalia gasped at the sight before her, her face bathed in a fiery red glow from the planet below. Its surface was clad in fire and metal, its atmosphere choked with striated clouds of pollution. Teeming with gargantuan sprawls of industry larger than the continents of Old Earth, the world seemed to throb with the heartbeat of monstrous hammers.