You will think me mad. A bearer of drivel, a wayward oaf dreaming of horror when my mind should be fixed upon the Emperor’s glory. But I assure you that my story is real, and I stand before you as the portent of our doom if you do not heed my words. Please, listen, for the good of us all.

I will start with a question. Have you ever visited 18-THIA-47? I hadn’t before I met the Magus. Arbitrators such as I seldom find business in such dissolute districts. But there it was, delivered by hand to my superiors, a summons from a person called Magus Kreel, along with the condition that I must be the arbitrator who responded to her call.

Despite providing no indication of the nature of her request, nor the reason why it should invoke me, I was quite content to honour it. Indeed, along with the considerable personal reward the summons promised, I was also moved by the chance to visit such a storied place as Thia, as it is colloquially known. You do not know it? Why, Thia is one of Selvanus Binary’s most ancient centres! Under its broken spires lie the remains of our first factoria, and down through its countless levels, hardened hands have toiled over millenia for the betterment of us all. A fascinating place indeed.

I admit that I soon regretted my enthusiasm. Four days passage by a bewildering and tedious number of inter-hive transports will dampen even the most ardent interest. But the journey was at least a chance to research the figure who’d summoned me. My firm’s archive-servitors sent me records on Magus Kreel by noosphere as I travelled, and while I discovered nothing on the Magus herself, there was more on her illustrious family, being peppered with high-serving Imperial administrators who stretched far back into Selvanus Binary’s better days. The strange thing, however, was that the last mention of her lineage was two centuries old.

I dismissed this information, cognisant of the increasingly negligent nature of our city’s administrators and scribes. Besides, while my client remained mysterious, she proved decorous, sending me a vox-cast as I travelled. I recall it perfectly. “My friend,” it began. “In anticipation of our opportunity to welcome you to Thia, we are anxiously preparing for your presence.”

She went on to detail the means by which I would proceed from the transport hub to her palace. I was to meet her representative on the concourse, and indeed, they were waiting as I arrived, a welcome sight after the privations of the journey, even if their face and form remained entirely concealed beneath a carmine cloak, and they moved with an oddly sinuous gait. I did not take much notice, however. My mind was rather fixed on the hospitality the Magus had seemed to promise and on my relief that I would not be facing the dangers of walking alone through Thia’s twisted and decaying alleyways. The figure never uttered a word to me, and I was gratified by the efficiency of its guidance.

With all that has passed since, I know I should have heeded every warning coded in the Magus’ mystery. But even now I cannot be angry at myself. Few opportunities for wonder and curiosity remain on this sad world, and, Throne, you should have seen her palace. Such grand scale is common in the Golden Spire, of course, but never had I realised it could lie in the hab-warrens of a place like Thia. Bounded by rockcrete walls which stretched into the dim fog of the vaults above, this place was old, evidenced by the cracked slabs that paved the by-ways and walls which at body height were smooth, almost glossy, as if brushed by numberless hands. To the better classes of our planet, this was undiscovered history!

But as I gazed upon the palace’s shadowed windows, I noticed the bizarre quiet in which I stood. Here, even as it was pressed in by teeming warren life, the palace sat in solitude. And yet – watchfulness… Was that a movement in an upper casement? I was quite distracted, enough that I didn’t notice that my companion had left me and another had come.

“Welcome, arbitrator. This is an auspicious day.” The Magus had emerged from the palace to meet me.

Her eyes were what I remember best. I could barely perceive anything else. They bore into me, cold and hungry, deep enough that it felt as if they saw my thoughts. As I stood there, transfixed, she began to tell me how we would produce profound and wonderful things together, that my particular skills were indispensable. I felt warm, entranced, and she took my arm with a grip of unexpected steel and pulled me towards the dark of the palace’s open door. I knew, even then, that I would give her whatever she asked.

We entered the palace’s entrance hall. It was a large and dusty chamber ringed with ornate furniture, but as I neared it I noticed it was scuffed and worn. At the chamber’s centre stood a large table, strewn with papers. I was thirsty and hungry, but it was clear the work was to begin, then and there. These papers, the Magus explained, documented the extent of her estate. My task was to help her move to the Golden Spire, where she said she would better exercise her aristocratic connections with the high-caste administrators who live and work there. Thus, I was to exercise my legal talents to procure her a hab which befitted her station, and to organise the conveyance of her household to it.

Her requirements were specific. It must be located in the select upper three-quarters of the spire and yet have excellent connections to the underhive. It needed at least six interior rooms of large dimension and a minimum of four exits, one of which must connect to the exterior, and one which must be little overlooked.

Now I understand her design. It would allow her – and her household – to gather and disperse without detection inside the heart of our elite. But then I was too stupefied to grasp it. My only question was why she needed an arbitrator to perform a task which could be quite easily performed through servitor-agents. But even before I finished my sentence, she curtly answered.

“Our works will not be defiled by the touch of those –” Her face, previously so serene, flashed momentarily with disgust. “Debased vessels.”

I worried that she was aware of my binaric connection to my firm’s servitors, and perhaps she caught my panic, for she then expressed a smile which sent me spiralling into helpless rapture and said, “You are all I need.”

And so I began. Screeds of data were transmitted to me: deeds, iso-schema, inventories. I presented each option to her, coveting the tiniest praise. I have the vaguest recollection of scuttling things in the corners of the room, but I was uncommonly driven, intently focused on my – her – work.

I do not know how long it was before she reappeared, bearing a tray with a cup of red liquid, to tell me that I would not be leaving at our arranged time. She assured me that the work was vital and spoke of my superiors by name and with familiarity. They had apparently approved my long-term sequestration. But the spell I’d fallen under lifted just enough for the strangeness of my situation to become apparent. I remember a rising sense of threat, and stammering something to her about my other clients and how they were also in need of my services, but swift as a snake and with uncommon strength, she stepped forward and pressed the cup to my mouth.

I started, my reverie fully broken, as the liquid inside burned my lips. I tried to spit it out, but Throne, she turned! Her face flared into a countenance of rage such as I had never seen before. “You will stay,” she hissed, and I found myself swallowing. The liquid seared its way down my throat and I felt my resistance dissolving. She left me surrounded by my papers.

From then it was as if a mist had descended upon me, but I know I continued to work. I filed covenants and signed contracts. I recall fragments of each document, but few details. I chartered transports and haul-units. I think there were others there, whispering things to me which I cannot bear to attempt to remember. And then, nothing.

I awoke alone, lying on my back in the deserted palace. My body was burning. I presume she had left me for dead, my purpose exhausted. And then I noticed, cut into the bowed plasteel ceiling above me, a symbol of a coiled xenos form, its back ridged with droplets. That was when I finally understood what I had done.

A nausea such as I’ve never felt before washed over me. I vomited red ichor over the flagstones, my chest heaving over and over in wretched pain until there was nothing left. It’s probably what saved me. But I did not care. I’d opened all I loved to corruption. Exposed the heart of our society to wretched xenos infection.

From the floor of that place, so lost in Thia’s ancient depths, I could only speculate at what would follow. But I mustered my strength and now, here I am before you. The Magus’ evil must now be all around us, here in the Golden Spire. We must act, before –

No. No, no. You? You are with her? She is everywhere! Throne save us all.