Tilting her primary feathers a fraction higher, she tightened the circle she was flying in, bringing her closer to the figures at the square’s edge. With luck, they would be too involved with their argument to notice her sliding by, lost in the shadows of the Undrentree’s lower branches.

As Liska came around, she could see Edda in more detail. His face looked human, trapped inside the wooden statue of his body. Although there were bark-like whorls and bumps all over his skin. His eyes glowed from deep pools of shadow under his mossy brows, and she spotted the brush of a squirrel, scurrying around in his beard.

The arbomancer was still yelling, and now she could pick up some of the words.

‘. . . foolish not to try! What else are we to do? Wait for the rot to reach the Undrentree? Let the minions of Bitterblight walk right into our city and destroy everything we have created?’

The rot. Liska couldn’t stop a snarl slipping from her mouth.

That was what lurked to the west of the mountains. The greatest threat of all that the city faced. There, amongst the blackened, drained soil, was another tree: sister of the one that nurtured all of Arborven. Bitterblight. Nobody had ever seen it, or at least lived to tell the tale. But legends described it as a dark, shapeless thing. A void of emptiness more like a hole in the universe than a tree. Jagged scratches instead of branches. Black, flapping streaks of nothing instead of leaves. A stinking, toxic thing – opposite to the Undrentree in every way.

It killed instead of cared; destroyed instead of created. Its roots drained energy from the world, spewing it out again in the form of grey fungus and seeping, living oil. Poisons that spread ever outwards, hungry to reach the Undrentree itself and suck it dry.

Edda moved his head from side to side in a slow, ponderous shake. When he spoke, his voice creaked like branches rubbing together in the wind. It echoed as if it had travelled up from roots lost deep under the ground.

‘The power of the shadow tree cannot be harnessed. It is not for us to touch. Our law forbids it. Any creature who tries to use or control it will be destroyed by it in the end. This is known. This has always been known.’

The robed arbomancer shook his head. Liska had arced round behind Edda now and could see the mage’s face. Pale skin, bald head. Dark eyes that flashed with anger.

‘But nobody has even tried! My research shows that it might be possible. That the rot from Bitterblight can be channelled . . . used . . . made to work for us, even! Wouldn’t it be worth an attempt at least? Imagine if we no longer had to worry about the Undrentree being killed off? What if we controlled its armies and were able to use them against the wyverns and the Poxpunks?’