like a buzz, like tinnitus, but it seldom went away. The people of the interex called it the aria, and it was a fundamental part of their communication. They still used language - indeed, their spoken language was an evolved human dialect closer in form to the prime language of Terra than Cthonic - but they had long ago formulated the aria as an accompaniment and enhancement of speech, and as a mode of translation.

Scrutinised by the iterators during the voyage, the aria proved to be hard to define. Essentially, it was a form of high mathematics, a universal constant that transcended linguistic barriers, but the mathematical structures were expressed through specific harmonic and melodic modes which, to the untrained ear, sounded like music. Strands of complex melody rang in the background of all the interex's vocal transmissions, and when one of their kind spoke face to face, it was usual to have one or more of the meturge players accompany his speech with their instruments. The meturge players were the translators and envoys.

Tall, like all the people of the interex, they wore long coats of a glossy, green fibre, laced with slender gold piping. The flesh of their ears was distended and splayed, by genetic and surgical enhancement, like the ears of bats or other nocturnal fliers. Comm technology, the equivalent of vox, was laced around the high collars of their coats, and each one carried an instrument strapped across his chest, a device with amplifiers and coiled pipes, and numerous digital keys on which the meturge player's nimble fingers constantly rested. A swan-necked mouthpiece rose from the top of each instrument, enabling the player to blow, hum, or vocalise into the device.

The first meeting between Imperium and interex had been formal and cautious. Envoys came aboard the Vengeful Spirit, escorted by meturge players and soldiers.

The envoys were uniformly handsome and lean, with piercing eyes. Their hair was dressed short, and intricate dermatoglyphics - Loken suspected permanent tattoos - decorated either the left or right-hand sides of their faces. They wore knee-length robes of a soft, pale blue cloth, under which they were dressed in close-fitting clothing woven from the same, glossy fibre that composed the meturge players' coats.

The soldiers were impressive. Fifty of them, led by officers, had descended from their shuttle. Taller than the envoys, they were clad from crown to toe in metal armour of burnished silver and emerald green with aposematic chevrons of scarlet. The armour was of almost delicate design, and sheathed their bodies tightly; it was in no way as massive or heavy-set as the Astartes' plate. The soldiers - variously gleves or sagit-tars, Loken learned - were almost as tall as the Astartes, but with their far more slender build and more closely fitted armour, they seemed slight compared to the Imperial giants. Abaddon, at the first meeting, muttered that he doubted their fancy armour would stand even a slap.

Their weapons caused more remarks. Most of the soldiers had swords sheathed across their backs. Some, the gleves, carried long-bladed metal spears with heavy ball counterweights on the base ends. The others, the sagit-tars, carried recurve bows wrought from some dark metal. The sagittars had sheaves of long, flightless darts laced to their right thighs.

'Bows?' Torgaddon whispered. 'Really? They stun us with the power and scale of their vessels, then come aboard carrying bows?'

They're probably ceremonial.’ Aximand murmured.

The soldier officers wore serrated half-discs across the skulls of their helmets. The visors of their close-fitting helms were all alike: the metal modelled to the lines of

brow and cheekbone and nose, with simple oval eyeslits that were backlit blue. The mouth and chin area of each visor was built out, like a thrusting, pugnacious jaw, containing a communication module.

Behind the slender soldiers, as a further escort, came heavier forms. Shorter, and far more thick-set, these men were similarly armoured, though in browns and golds. Loken supposed them to be heavy troopers, their bodies gene-bred for bulk and muscle, designed for close combat, but they carried no weapons. There were twenty of them, and they flanked five robotic creatures, slender, silver quadrupeds of intricate and elegant design, made to resemble the finest Terra-stock horses, except that they possessed no heads or necks.

'Artificials.’ Horas whispered aside to Maloghurst. 'Make sure Master Regulus is observing this via the pict feed. I'll want his notes later.’

One of the flagship's embarkation decks had been entirely cleared for the ceremonial meeting. Imperial banners had been hung along the vault, and the whole of First Company assembled in full plate as an honour guard. The Astartes formed two unwavering blocks of white figures, rigid and still, their front rows a glossy black line of Justaerin Terminators. In the aisle between the two formations, Horus stood with the Mournival, Maloghurst and other senior officials like Ing Mae Sing. The Warmaster and his lieutenants wore full armour and cloaks, though Horus's head was bare.

They watched the heavy interex shuttle move ponderously down the lighted runway of the deck, and settle on polished skids. Then hatch-ramps in its prow opened, the white metal unfolding like giant origami puzzles, and the envoys and their escorts disembarked. In total, with the soldiers and the meturge players, there were over one hundred of them. They came to a halt, with the envoys in a line at the front and the escort

arranged in perfect symmetry behind. Forty-eight hours of intense intership communication had preceded that cautious moment. Forty-eight hours of delicate diplomacy.

Horas gave a nod, and the men of First Company chested their weapons and bowed their heads in one, loud, unified motion. Horus himself stepped forward and walked alone down the aisle space, his cloak billowing behind him.

He came face to face with what seemed to be the senior envoy, made the sign of the aquila, and bowed.

1 greet you on-' he began.

The moment he started speaking, the meturge players began sounding their instruments softly. Horus stopped.

Translation form.’ the envoy said, his own words accompanied by meturge playing.

'It is disconcerting,' Horus smiled.

'For purposes of clarity and comprehension.’ the envoy said.

We appear to understand each other well enough.’ Horus smiled.

The envoy nodded curtly. Then I will tell the players to stop.’ he said.

'No.’ said Horus. 'Let us be natural. If this is your way.’

Again, the envoy nodded. The exchange continued, surrounded by the oddly melodied playing.

'I greet you on behalf of the Emperor of Mankind, beloved by all, and in the name of the Imperium of Terra.’

'On behalf of the society of the interex, I accept your greetings and return them.’

Thank you.’ said Horus.

'Of the first thing.’ the envoy said. You are from Terra?'

Yes.’

'From old Terra, that was also called Earth?'

Yes.’

This can be verified?'

'By all means.’ smiled Horns. "You know of Terra?'

An odd expression, like a pang, crossed the envoy's face, and he glanced round at his colleagues. We are from Terra. Ancestrally. Genetically It was our origin world, eons ago. If you are truly of Terra, then this is a momentous occasion. For the first time in thousands of years, the interex has established contact with its lost cousins.’

'It is our purpose in the stars.’ Horns said, 'to find all the lost families of man, cast away so long ago.’

The envoy bowed his head. 'I am Diath Shehn, abbro-carius.’

'I am Horus, Warmaster.’

The music of the meturge players made a slight, but noticeably discordant sound as it expressed 'Warmaster'. Shehn frowned.

'Warmaster?' he repeated.