The adept either didn't notice or believed she already knew him, and passed on his way with a final canted burst of annoyance. Dalia let out a pent-up breath and turned as the sleeve of her robe was tugged.

'If you're quite finished?' said Caxton, looking in alarm at the adept's retreating back.

'Yes, sorry,' she said.

'The mag-lev hub is just ahead,' said Zouche, pointing to a bronze archway through which hundreds of people were passing back and forth. Dalia experienced a moment of sickening realisation when they reached the archway and she saw the wide steps descending hundreds of metres into the bedrock of Mars.

'They're going to have to go below the level of the magma?' she asked.

'Of course,' said Caxton. 'The mag-lev can't exactly go through the lava now can it?'

'No, I suppose not,' said Dalia, wishing she hadn't said anything.

Caxton pulled her on and she quelled her mounting panic as they began their journey downwards. Sizzling lumen strips that flickered and hurt Dalia's eyes illuminated their route along a tunnel thronged with workers making their way to and from their shifts. They marched like automatons - one side ascending, the other descending - all in perfect unison towards or from the metropolis above.

Zouche forged them a path downwards with his squat frame and robust language, and anyone who objected to either soon bit their tongue at the sight of his thunderous stare and bunched fists.

Eventually they reached the bottom, the transit station itself, a gigantic hangar with a colossal vaulted ceiling. There seemed to be no order to the movement of the packed mass of people, just heaving bodies that moved according to tidal patterns rather than with any purpose.

Robed Protectors bearing crackling weapon-staves and the four-by-four number grid symbol of Adept Zeth policed the energetic scrum of workers, and Dalia tried to avoid looking at them for fear of attracting their attention. Servo skulls bobbed overhead, and grating binaric code spilled from vox-plates set into the walls, announcing departures and arrivals and warning travellers to beware of the void between mag-lev and platform.

'Now where?' asked Dalia, unable to make sense of the overlaid binary instructions blaring from the vox.

'This way,' said Zouche pushing through the crowds. 'It looks harder than it is, but after you've ridden the mag-lev once it's easy to find your way around.'

'I'll take your word for it,' said Dalia, taking Caxton and Severine's hands like children on a scholam outing as they set off after him.

Zouche led the way through a confusing series of ceramic-tiled tunnels until they stood on a crowded platform with hundreds of tired-looking workers.

Distorted, wavering blurts of code fragments coughed from battered vox-amps set in wooden boxes mounted on the ceiling, and even Zouche shrugged when Dalia looked at him for an explanation.

'I didn't get a word of that,' said Zouche.

'It said the next mag-lev will be delayed by two hundred and seventy-five seconds,' said a powerful voice behind them.

Dalia flinched at the sound, recognising the harsh, metallic rasp of a human voice issuing from behind a bronze mask.

She turned and looked up into a pair of glowing green eyes.

'Greetings, Dalia Cythera,' said Rho-mu 31.

The enemy Reaver was burning, the top portion of its carapace blown away by Cavalerio's blastgun after a punishing barrage from the Vulcan had stripped it of its voids. He felt the heat build in his left arm as the weapon recharged, and a clatter in his right as the autoloader recycled the mega bolter to fire again.

The enemy engine toppled backwards, flattening an ore silo and sending up a blizzard of flame and smoke. Crushed rockcrete dust billowed from its demise and even as Cavalerio exulted in the kill, he knew the other Reaver was still out there, lurking behind the burning ruins of the refinery, using the smoke and heat to mask its reactor bloom.

'Moderati, get me a mass reading!' he ordered in a squirt of binary.

'Yes, princeps.'

Information flooded him through the Manifold, a hundred different stimuli collected from the mighty engine's myriad surveyors: heat, mass, motion, radiation, vibration and shield harmonics. Everything combined to paint a world more real to Cavalerio than reality itself.

He drank the liquid data down, swallowing and digesting it in a heartbeat. His awareness of his surroundings bloomed and he saw the enemy Reaver manoeuvring around the refinery, smashing its way through the walls and roof beams of the nearby steelworks.

A flicker of heat and mass tugged at his awareness and he felt the stealthy approach of the enemy Warhound before he saw it.

'Steersman, reverse pace, flank speed! Heading two-seven-zero!'

A Warlord Titan was not built for rapid course changes, but the steersman was good and the engine obeyed with commendable speed. The building beside Cavalerio exploded into a mass of shredded girders, torn concrete slabs and sheet metal roofing. Clouds of vaporised rockcrete billowed, but Cavalerio's engine-sight could penetrate it without difficulty.

He saw the Warhound, a graceful loping predator of red and silver, dart from the shadows of a collapsed forge-hangar, its turbos blitzing with hard light. Cavalerio felt the impacts on his shields, but its angle of fire was poor and most of the shots were void-skidding.

he canted.

'Yes, princeps.'

'Moderati, firing solution!'

The Warhound was nimble, but it had struck too soon, and without the shock value of its turbo lasers impacting on its target's shields it was vulnerable. Data inloaded from the moderati's station, and Cavalerio saw the vectors of fire slide into his mind at the speed of thought. He felt the wordless bray of the gun-servitor's acknowledgement and opened fire.

A sheeting storm of explosive rounds roared from Cavalerio's mega bolter, obscuring the Warhound in a blizzard of detonations and flaring shreds of discharging voids. The Warhound staggered, pushed back against the brick walls of a weapon shop. Stone and steel tumbled to the ground, but Cavalerio knew the enemy engine wasn't out of the fight yet.

'Steersman, move in! Moderati, arm missiles. Sensori, where's that Reaver?'

'Moving in, aye!'

'Missiles arming!'

'Reaver still closing, princeps. Six hundred metres, bearing zero-six-three.'

Cavalerio's engine closed the gap between it and the Warhound. He had to kill it before the Reaver was in a position to help. Individually, neither of the enemy machines were a match for his Warlord, but working together, they could potentially bring him down if he were not careful.

The Warhound swayed as it picked itself up, its weapon limbs shaking like a dog climbing from the water. Its shields burbled and sparked, and Cavalerio read a flaring convergence of energy gaps clustered around the engine's hip.

Information updates sluiced around him and he updated his situational awareness, feeling the danger of the closing Reaver and knowing he didn't have much time.

'Moderati! As soon as that Reaver comes into view, hit its upper carapace with a barrage from the carapace launcher. Three missile spread, five second intervals.'

'Yes, princeps.'

'Gun-servitor Hellas-88, slave weapon to my command.'

The implanted servitor wordlessly acknowledged his order, and Cavalerio felt the reassuring weight and industrial motion of the mega bolter as though it were part of his flesh. It was reckless to take command of the weapon from the servitor, who could fire it far more effectively than he could, but to make this kill, he wanted to feel the thunder.

Cavalerio surrendered to the engine's killing lust, guiding it with his own need to defeat their foe. With a thought, the mega bolter engaged and sawed off a furious hurricane of shells at the staggering Warhound's wounded hip.