Unspeaking, they took the tunnel to their right, walked on through patches of darkness and light. Around them, the skittering of tiny legs, of sharp claws on stone. The tunnel got narrower. The first hints of claustrophobia crowded at the edges of Valkyrie’s mind. The first time she’d come down into these caves, they had been searching for the Sceptre of the Ancients. The second time, she’d been held captive by what was left of Anathem Mire. Her last trip down here had not been any happier. The memory of being dragged into a tightening hole, too narrow to even move her arms, slipped by her defences and she took a shallow breath. Then she caught herself, made her heart turn to steel, and she pushed the fear away from her. If Skulduggery noticed the slight hesitation in her step, he didn’t say anything.

Something brushed by her foot and she jumped back, clenching her jaw to stifle the scream. There was more skittering now, these little creatures drawn to the magic that held Skulduggery together. Valkyrie forced herself onwards, swinging her feet to kick them out of her way. Her boot connected solidly with some living thing of bloated but yielding mass, then another that was made of sturdier stuff, and the others seemed to get the message – stay out of the way of the girl in black.

They went over a bridge that crossed a chasm, out of which belched steam and cold winds that tossed Valkyrie’s hair and threatened to snatch her off the edge. Then they took a tunnel as wide and tall as a chapel but as long as a racetrack. The ground got slippery. Somewhere, the sound of running water, all gurgles and rush.

They got to another bridge, a narrower one, and Skulduggery stopped, his hand out, reading the air.

“Just once,” he said, “I’d have liked things to have gone without a hitch.”

On the other side, a creature emerged from the shadows.

The size of a small tiger, its grey and black fur was short and fine, and grew up around the protrusions of bones at its joints and around its skull.

“Mire had a name for these things,” Gordon whispered. “He called them Phalanx Tigers. They were responsible for the death of more than one expedition member.”

“Well, maybe this one’s friendly,” Skulduggery muttered.

The tiger padded slowly across the bridge, and Skulduggery went to meet it.

“Easy, girl,” Valkyrie heard him say as he raised his gun. “Just stay very still …”

The tranq gun whispered just as the tiger growled, and the dart bounced off its rows of teeth. Its multiple rows of teeth.