It was writing, two rows of large carved letters. Palemon strode up to it and frowned. ‘What does it say?’ he asked. ‘It looks like it was written in haste.’

‘It is Old Aleuthean. As you know, our language has changed over the years, but I believe it says: “The dragons are fierce.” That is the first line.’

‘And the next?’

‘“The Arch of Nisos brings doom upon the world.”’

He turned to her. ‘Dragons?’

‘Look around you.’

He spun round; there was nothing to see except the cages. He counted twelve of them, shrouded in darkness. Zara walked forward, bringing the light with her, and then he realized.

Some of the cages had occupants.

He strode to the nearest and stared inside, trying to understand what it was he was seeing. Zara followed him and threw the bolt, the metal creaking as she opened the cage. As Palemon entered, Zara’s fingers danced around the staff and the light grew brighter.

Approaching the thing that filled the cage, Palemon finally stopped in his tracks. He swallowed.

He was looking at the skeleton of a massive beast. An iron collar was fastened around its neck, just behind the immense, wedge-shaped skull. The skull was resting on the ground, with empty eye sockets, each able to accommodate a man’s head, and teeth yellowed with age. The curved spine was ridged like the trunk of a palm tree and led to wings made of countless delicate bones. A curled tail terminated in a diamond-shaped spike. Long claws at the end of its forelimbs looked sharp enough to decapitate a man with a single blow.

‘It’s a . . .’

‘A dragon,’ Zara said. ‘Look.’

She touched the end of her staff to the skull, and he now saw a large hole punched through the thick bone behind one of the eye sockets. ‘It was killed. They are all like this. Half of these cages contain a skeleton.’

Palemon tugged at his beard, trying to make sense of it.

‘I have suspicions about the purpose of the tower, but I think I know what this place underneath was,’ Zara said. Palemon glanced up when he heard her next words. ‘It was their stables. Only the animals they kept here weren’t horses.’

‘But how . . . Why . . . ?’

‘Look.’ Zara tilted her staff to point out something hanging from a hook on the wall.

At first he thought it was simply a length of old chain, but then the sorceress used the tip of her staff to lift up one of the coils of metal links, and he saw that the reddish metal didn’t look like iron.

‘Some kind of harness?’ Palemon asked.

‘They appear to be reins,’ Zara said. ‘There are five other skeletons, and five more sets like this, six in total. The metal is copper, a little corroded but serviceable. And undeniably magical.’