Seeing the energy of Arborven, feeling the static tingle of power in the air, Liska had thought – just for a moment – that they might simply tear through the seepers and win.

But that, she realised, had been stupid.

As powerful as her people were, their numbers were nothing compared to the sheer mass of the enemy.

The shadow tree’s forces waited until the treekeepers were well out on to the plain of rot, until their feet splashed through thick puddles of poisonous goo, and then they surged forwards.

Shrieking and howling, they rose up behind a waft of stink, boiling forwards like an exploding drain. Seepers piled on top of one another in waves, in crests, and crashed down on the treekeepers, swallowing them completely.

For a second Edda and the others were gone from sight, and then they burst free, lashing about themselves with their trunk-sized limbs.

The liquid bodies of seepers flew through the air all around, but there were always hundreds more to replace them.

Then gorgaunts stomped forwards, picking up handfuls of their smaller comrades and hurling them at the mages like deadly snowballs.

They crashed into the ranks, breaking spells, lashing out with their rubbery tentacles, causing massive damage everywhere.

The mages struck back with bolts of lightning from the gathered storm clouds. Their wooden golems fought tirelessly, hacking at the gooey creatures that swarmed all over them.

And from the sky, the shapewalkers swooped, biting and clawing, snatching and gouging. They flew around the gorgaunts in fierce swarms, aiming for their eyes, tearing at their legs and shoulders. More than one of the giants toppled over, crushing hundreds of seepers into liquid beneath them.

But none of it was enough.

For every enemy that was defeated, three more took its place. Nightmarish things tottered towards the treekeepers on spider legs, poisonous barbs and stingers flashing. Four-armed beasts with serpent bodies reared up, snatching shapewalkers from the sky as they flew past. Dragon-shaped masses of living fungus spat missiles upwards – great clods of grey jelly that burned flesh and melted armour.

‘There’s too many!’ Embla shouted. She had been swinging with her club fist as they marched, sweeping enemies out of their path. They were behind the main force of treekeepers, out of the thick of battle, but were still getting swarmed.

‘I’ll try to make a gap!’ Elowen called. She was moving her arms in patterns, casting hexes that hung in the air, glowing. Roots whipped all around them as they walked, tearing through seepers. Still some got through.

‘Take that!’ Fishbone yelled, slashing at a creature that had managed to clamber up Embla’s back. The thing dodged around the treekeeper’s neck, coming close to Liska, who held the heart up as a shield. Beams of light shot out from it, searing the seeper into dust.

‘Don’t let them see we have the heart!’ Elowen warned. ‘We have to slip through without them noticing!’