He nodded. ‘Follow the causeway,’ he confirmed. ‘In about thirty metres it hooks to the left and then angles downwards another ten or so. Keep flat to the wall and be mindful of your footing, the ledge is very narrow in places.’

‘Then where?’ It came out as a demand not a question. Kade’s fists bunched around the stock of his combat shotguns but he had at least released his grip on Illion’s shoulder. If not, he might have crushed his collar bone.

‘Keeps descending, down into a shallow basin of rock, I think. Couldn’t read it that well through the smoke.’

Kade regarded the pathfinder for a few more seconds, as if gauging whether he was satisfied with his guide’s assessment. In the end he turned away and started off down the causeway. ‘Follow, pathfinder,’ he called behind him.

‘Something has happened to him,’ said Za’tenga in a low voice.

Illion nodded to the other warrior at his shoulder then asked, ‘Har’gaan?’

Za’tenga was about to shake his head when Har’gaan staggered past them both.

‘Come on,’ he said, grimacing. ‘We are not dead yet.’ Har’gaan glanced over his shoulder, but his gaze went beyond the other two aspirants and he scowled. ‘We need to move. Now.’

Illion turned.

Fear had spurred Har’gaan’s limbs into a final desperate act of motion.

The aspirants were not the only ones seeking a way around the sea of fire. Three sinuous bodies, low against the sheer rock and climbing swiftly, followed them. The serrwyrms had caught up with their prey.

‘Down!’ Kade’s shout was almost as loud as his twin shotgun blasts as a storm of shrapnel erupted from their mouths. The muzzle flare was brief but sharp, so too the lead serrwyrm’s death scream as it plummeted off the fire canyon’s flank with only half a head.

The big Themian racked another shell into the breech. He was stalking forwards along the causeway, the others flat against it, advancing on the creatures.

‘Fight or die!’ he roared, triggering the cannons again, this time at a second pair who were scaling down the canyon’s summit from above.

Three las-carbines answered as the rest of the aspirants combined their fire to take down a third creature. Throughout the barrage, the serrwyrms slithered and weaved, and the fire canyon continued to break apart.

‘We cannot stay here and fight them all off.’ Illion had adopted a kneeling stance with the end of the carbine’s stock tucked into his armpit, up into the shoulder to better absorb recoil. Every shot was accurate, he had some skill as a marksman, but the serrwyrm’s chitinous armour was thick. Most of his shots were ineffective.

Behind him, Kade grunted.

‘How many left?’ he growled between shotgun blasts.

‘At least three, but there could be more,’ shouted Illion.