The west. Outside the mountains. The Rotlands.

‘Embla!’ Liska shouted. ‘Follow that sound! Quickly! There’s a battle going on – a battle for Arborven!’

Chapter 15

A sprinting treekeeper is an awesome sight to behold.

Embla leapt metres with each stride, heavy wooden feet crashing down on to the scree, smashing granite chips into sand.

Liska and the others clung on to her shoulders, their fingertips hooked around whorls of bark, hair streaming out behind them, wind whipping their faces.

They rounded the north-west mountains and turned south, looking out over the stretch of waste known as the Rotlands. A place that had already been consumed by the shadow tree – a taste of what was in store if they should fail.

The red dirt and stone of the desert they had just crossed was covered in layers of grey and black slime. Like tides of dark vomit, it hung in strands and dribbles from every rock and stunted tree.

Half-formed clusters of diseased toadstools were clumped everywhere like blisters. Fat blowflies buzzed around, feasting on the gloop, bathing in the stink. It was a scene straight from Liska’s worst nightmares, and it stretched all the way to the horizon, interrupted only by a single mound of earth. Some kind of stunted volcano with a crater at the top that wheezed out black smoke.

‘The smell!’ Liska clapped her hands over her nose. Fishbone’s eyes were watering and even Embla had to stagger to a halt.

‘What . . . what is this place?’ she asked, her wooden limbs beginning to tremble.

‘This is the realm of Bitterblight,’ said Elowen. ‘This is how the shadow trees want to shape the world.’

‘Big Mew’s hairballs,’ said Fishbone, coughing and spluttering. ‘It smells worse than a dead wolf’s toilet parts!’

Liska didn’t even hear him. Her attention was fixed on a crowd of figures gathered at the edge of the stinking rot. A massive crowd, thousands strong, facing out towards the sea of filth.

‘Look,’ she said. ‘It’s an army. Our army!’

Lug followed her gaze. ‘Nematus below,’ he said, his voice an awed whisper. ‘There must be every mage in Arborven there.’

‘But I fear it won’t be enough,’ said Elowen. ‘See what faces them . . .’

Liska tore her eyes away from her precious tree folk and looked across the plain. At first glance she had mistaken the heaving mass of grey ooze as part of the landscape. Now she could see it was moving, seething.