A tendril appeared first. Like the first shoot of a plant or tree, sightlessly feeling its way around its new world. Except this one was made of shadowy darkness. A dark grey, flowing liquid, wisps of smoke seeping from its edges.

‘It’s true!’ Liska fought back the urge to scream. ‘Everything I heard him say at the Undren Square! I knew the city was in danger! I knew it!’

‘The rot . . .’ Lug could only manage a strangled whisper. ‘He’s bringing the rot inside the city. That thing is a seeper . . .’

More of the sludge emerged. The tar-like goo had formed itself into a humanoid shape. A featureless head, writhing grasping arms that slapped and stuck to the stone as it hauled itself through. It lurched and wobbled as it moved, stretching itself then shrinking, so that one moment it was taller than the mage that summoned it, the next half his size.

Others filled the tunnel behind it and Noxis beckoned them onwards, out on to a path that led down the mountainside towards the Scrubbings and into Arborven. The second walked on all fours like a beast, the third had seven or eight limbs that waved in the air as it shuffled and slithered along. They were formed differently but all were made of the same slimy, oozing goo.

‘It’s a sneak attack,’ said Liska. ‘He’s smuggling those things in to kill the treekeepers!’

‘Bitterblight must have cast a spell on him,’ said Lug. ‘Possessed him. Made him turn against us. That’s why it’s forbidden to experiment with rot. That’s why the treekeepers were furious with Noxis!’

‘The shapewalkers won’t have seen him,’ said Liska. ‘They only expect attacks to come over the mountains. We have to warn everybody. Raise the alarm . . .’

She looked back into the forest. The Undrentree was so far away . . . by the time she reached it, there would be a whole flood of rot creatures pouring down from the tunnel.

Then she looked upwards, up where the clouds hid the broken fortress. There were hundreds of shapewalkers up there, primed and ready for battle . . .

‘Lug!’ She pulled her new friend towards her, making him look away from the horrors that were frothing out of the tunnel mouth. ‘I have to fly up to the fortress and sound the alarm. You need to warn the treekeepers. Run back to the Undrentree, shouting all the way. Get the mages to come here. We have to stop Noxis before he lets too many of those things through!’

‘Yes,’ Lug stammered. ‘R-right.’ He looked as though he might be about to turn his robe an even deeper shade of brown. But Liska didn’t have time to worry about him. She pulled her hood over her head and dropped forwards, letting her cloak fall around her shoulders. The pull of the animal skin called her, washing over her until she felt herself begin to melt away . . .