“There is a lesson here,” he said. “It will do us good to face this without our powers. We have become lax in making war as it was once made.”

“Always the teacher, eh?” said Phosis T’kar.

“Always,” agreed Ahriman, “and always the student. Every experience is an opportunity to learn.”

“So what lesson can I possibly learn here?” demanded Hathor Maat. Of them all, Maat had the greatest dread of powerlessness, and the walk into the Mountain had tested his courage in ways beyond what they had faced before.

“We depend on our abilities to define us,” said Ahriman, feeling the bass vibration of the drums through the soles of his armoured boots. “We must learn to fight as Astartes again.”

“Why?” demanded Hathor Maat. “We have been gifted with power. The power of the Primordial Creator is in all of us, so why should we not use it?”

Ahriman shook his head. Like him, Hathor Maat had faced the Dominus Liminus, but his mastery of the Enumerations was that of Adept Major. He had achieved self-reliance, but he had yet to achieve the oneness of self and ego-extinction that would allow him to reach the higher Enumerations. Few Pavoni could, and Ahriman suspected Hathor Maat was no exception.

“You might as well send us in unarmed and say we should fight with our bare hands,” continued Hathor Maat.

“Someday you may have to do just that,” said Ahriman.

THE GROUND, WHICH had been steadily rising for the last hour, began to climb ever more steeply, and the sound of drums grew louder, as though amplified by the soaring walls of the valley. As it always was, Ahriman’s gaze was drawn up the incredible height of the mountain. The summit was hidden from view by its sheer mass, an endless slope rearing into a cloudless, yellow sky that was darkening to burnt orange.

It seemed inconceivable that this towering peak had been raised by natural means. Its proportions were too perfect, its form too pleasing to the eye, and its curves and lines flowed with a grace that was wholly unnatural. Ahriman had seen such perfect artifice before.

On Prospero.

The Vitravian pyramids and cult temples of Tizca were constructed using golden means and the numerical series of the Liber Abaci. Their work had been distilled and refined by Magnus the Red to fashion the City of Light with such beauty that all who beheld it were rendered speechless with delight.

Everywhere Ahriman looked he saw evidence of geometric perfection, as though the mountain’s creator had studied the divine proportions of the ancients and crafted the landmass to their design. Spiral patterns on the ground described perfect curves, pillars of rock were equally spaced, and each angle of cliff and cleft was artfully arranged with mathematical exactitude. Ahriman wondered what cause could be so great as to require such magnificent feats of geomorphic sculpting.

The mouth of the valley funnelled the sound of drums towards them, the beats rising and falling in what, at first, seemed a random pattern, but which Ahriman’s enhanced cognitive processes quickly discerned was not random at all.

“Prime armaments,” he ordered, and fifty weapons snapped up in unison, a mix of storm bolters, flamers and newly issued rotary cannons capable of unleashing thousands of shells per minute. Their official designation was assault cannon, but such a graceless name had none of the power of its former incarnation, and numerological study had led the Thousand Sons to keep its previous title: the reaper cannon.

The Mechanicum had not the wit or understanding to recognise the power of names or the mastery and fear a well chosen one could instil. With six letters, three vowels and three consonants, the reaper’s number was nine. Given the organisation of the Thousand Sons into a Pesedjetof nine Fellowships, it was a natural fit and the name had remained.

Ahriman recited the mantras that lifted his mind into the lower Enumerations and calmed his supra-enhanced physiology, allowing him to better process information and react without fear in a hostile environment. Normally this process would enhance his awareness of his surroundings, the essential nature of the world around him laid bare to his senses, but on this mountain the landscape was dead and lifeless to him.

Ahriman saw the diffuse glow of torches and fires ahead. The vibration of the ground was like the heartbeat of the mountain. Was he an ant crawling on the body of some larger organism, insignificant and easily swatted aside?

“Zagaya,” said Ahriman, and the Sekhmet formed a staggered arrowhead, with him at its point. Other Legions knew this formation as the speartip, and though Ahriman appreciated the robust, forceful nature of the term, he preferred the ancient name taught to him by the Emperor on Terra at the island fortress of Diemenslandt.

Phosis T’kar moved alongside him, and Ahriman recognised the urge for violence that filled his fellow captain. In his detached state, Ahriman wondered why he always called Phosis T’kar his “fellow” and never his “friend”.

“What are our orders?” asked Hathor Maat, tense and on edge.

“No violence unless I order it,” said Ahriman, opening the vox to the Sekhmet. “This is a march of investigation, not of war.”

“But be ready for it to become a war,” added Phosis T’kar with relish.

“Sekhmet, align your humours,” ordered Ahriman, using his mastery of the Enumerations to alter his body’s internal alchemy. “Temper the choleric with the phlegmatic, and bring the sanguine to the fore.”

Ahriman heard Hathor Maat muttering under his breath. Normally a Pavoni could balance his humours with a thought, but without access to the aether, Hathor Maat had to do it like the rest of them: with discipline, concentration and self-will.

The valley widened, and Ahriman saw a host of figures standing at the crest of the slope, like the legendary warriors of Leonidas who fought and died at Thermopylae. Ahriman felt nothing for them, no hatred and no fear. In the lower Enumerations he was beyond such considerations.

With their sunset-coloured robes, baked leather breastplates and long falarica, the Aghoru warriors were the very image of the barbarian tribes of ancient Terra. The warriors were not facing down the valley to repel invaders, but were instead focussed on something deeper in the valley and beyond his sight.

Ahriman’s fingers flexed on the hide grip of his bolter. The warriors above turned at the sound of the Sekhmet’s advance, and Ahriman saw they were all wearing masks of polished glass. Expressionless and without life, they resembled the gold leaf corpse masks placed upon the faces of ancient Mycenaean kings to conceal the decay of their features.

At the most recent conclave of the Rehahti, Magnus had had invited Yatiri, the leader of the Aghoru tribes gathered at the Mountain, to speak with them. The proud chieftain stood in the centre of Magnus’ austere pavilion, clad in saffron robes and wearing the ceremonial mirrormask of his people. Yatiri carried a black-bladed falarica and a heqa staff, not unlike those carried by the captains of the Thousand Sons. Though centuries of isolation had separated his people from the Imperium, the regal Yatiri spoke with clarity and fluency as he requested they refrain from entering the valley, explaining that it was a holy place to his people.

Holy. That was the word he had used.

Such a provocative word would have raised the hackles of many Astartes Legions, but the Thousand Sons understood the original meaning of the term – uninjured, sound, healthy – and rose above its connotations of divinity to recognise it for what it truly meant: a place free of imperfection. Yatiri’s request had roused some suspicion among the Legion, but Magnus had given his oath that the Thousand Sons would respect his wishes.

That request had been honoured until this moment.