They attacked as the Rout were crossing one of the ship's vast, lateral canyons. It was a cavernous space running down the neck of the ship far below the spinal way of the uppermost levels, but serving the same purpose of facilitating transit between the far-flung sections of the enormous vessel. Long steel lines for cable cars hung from pylons, and a monorail track ran dead down the centre. Bundles of cabling and pipes of all diameters clustered the sides of the chasm. But nothing moved there. Although there was no sign of direct damage, the heavy feeling of dereliction clung to the chasm. Giant, toothed blast doors had sealed the way into discrete sections. A lake of dark, stinking liquid had gathered in the chasm's base, steaming noxious vapours, and this deep in the ship the current battle was noticeable only as intermittent tremors that rippled the lake's surface.

Russ suddenly halted at the edge of a dusty bridge. He sniffed the air suspiciously, and waved his men back. The primarch looked up at the metal cliffs of the far side, scanning the open transitways and foot galleries for movement.

In the gloom there, metallic sea-green flashed between thick support pillars.

'I see them. They are coming. Take up position there.' He directed a group into the transit tunnel on the near side of the road, away from the advancing Sons of Horus. 'And you, get up into the upper galleries. Cover the far side, they will come at us in force here.'

The Vlka Fenryka's vox-net, near silent for a while but for distance count-offs and report calls, burst into sudden life.

Gunfire exploded from the far side of the canyon. Their ambush anticipated, the Sons of Horus attacked.

Horus' warriors approached in three trident prongs. The lead attack was offset from the other two, coming from the stem on the same side as the Rout along a wide, hexagonal supply route whose outer edge was open to the chasm. The route's rail trades were rusting, and detritus had been dumped in heaps along its length. Radioactive contaminants in the waste upset augur scans, so the traitors had been able to draw close without alerting their quarry. The first notice the Rout had of their presence was a sheeting blaze of reaper cannon fire that hammered two Wolves down, scattering their remains in a hail of white-hot shrapnel and blood. A trio of Contemptor Dreadnoughts moved steadily up the tracks, laying down such a volume of fire the junction quickly became impassable.