After Shand and Ussarine were hurled away in the gate, Aviel dared not remain in Carcharon. She and Wilm gathered food, water bottles, weapons and camping gear from the four frozen bodies in the yard. One body had a small coil of rope; he took it as well.

“Where can we hide?” said Aviel.

“Llian mentioned a way station further up the ridge,” said Wilm. “It’s out of sight of the tower; maybe Unick doesn’t know it exists.”

He made a ladder with the rope so they could climb down the rear wall. Aviel found it hard going. The way station turned out to be a tiny hut, ten feet by nine, built from slabs of shiny schist. It had a fireplace, a rough stone floor, no furniture and no window. Wood was stacked between the chimney and the wall. The door, though draughty, was sound.

Wilm lit the fire. Aviel put the food and water bottles near the heat to thaw. They ate and sat together, warming their hands on mugs of tea. Wilm kept looking at her sideways as if he did not know what to make of her. She was not the girl she had been when he left Casyme.

She was also mindful that he had made a friend in Chanthed and they had worked together to rescue Llian, then Unick had murdered her in front of him. Wilm must be angry and confused, and perhaps he felt guilty that he had not been able to save her.

Aviel was not confused about anything. She had expected to die a dozen times in the past weeks, and she knew exactly what she wanted: to rid the world of the stone and, if she survived, master the art of making scent potions.

“You look exhausted,” she said. “Get some sleep.”

“Do you want me to bind your ankle?”

“No!”

“Sorry,” he said hastily. “Just trying to help.”

“I’m used to doing everything for myself.”

He hunched his shoulders and stared at the fire. “What are we going to do about the stone?”

“I haven’t thought it through yet.”

“I don’t suppose you need my help with that either.”

Aviel realised that she was being mean-spirited. He had come all this way to save her from a brute, at great cost to himself. She did not like to touch, as a rule, but he was her oldest friend. She took his big hand and even drew some comfort from it.

“I’m really sorry, Wilm. Look, I don’t need the sleep, but you do. Why don’t we talk about it when you wake up?”

He took off his boots and lay down in his blankets. Aviel got out the grimoire and moved closer to the fire. The small, squashed writing was hard to read by the flickering light. She studied the Electuary of Compulsion. Could she compel Unick to destroy the stone that meant everything to him?

Ultimately, all forms of attacking mancery came down to a contest of wills, and his whole life had been a contest: himself versus the world. As for her, from the day she was born it had been her versus her six sisters, and her father, and everyone she had ever met save Wilm and Shand. Being crippled, overworked, underfed and chronically unlucky, her inner strength had to be all the stronger. She had to beat him.

Wilm was asleep, one fist clenched around his blankets. No one could have had a better friend. She smiled, rubbed salve into her swollen ankle and took up the grimoire.

Immersed in the work as she was, the night and the next day passed swiftly. The instructions for making the potion were complex and difficult, and made doubly so because she did not have all the scents she needed and had no way of making them here. She had to substitute them with ones she did have, but first she had to work out exactly how to use them and in what order, otherwise the completed potion could prove fatal.

“What are you doing?” said Wilm the following mid-afternoon.

Aviel sniffed the phial she was using, added another drop, sniffed again and frowned. “Step nine requires oil of bergamot and I don’t have any. I’m trying to make a substitute with lemon and almond oils, plus a hint of lavender and a few other things, but it’s not working. I’ll have to start afresh.”

“You’re so clever,” he said. “I wouldn’t be game.”

“Says the man who taught himself how to use a sword then beat Snoat’s best assassin.”

She might have said killed but Aviel did not want to think about that.

“How long is it going to take?” said Wilm.

“Another day or two – if we get that long. The drumming is getting louder.”

“It was in my dreams the whole time I was asleep. Is there anything I can do to help?”

“Not really.”

“Then I’ll go and spy on Carcharon.”

Fear shivered through her. “Be careful.”

The next day passed, and the day after. The drumming grew ever louder, reminding Aviel that her work was urgent, but whenever she tried to hurry she made mistakes and had to do it all over again.

That evening the scent potion was finally done, and she knew it was as close to the true Electuary of Compulsion as she could make it. But would it work? There was no choice but to try it on Unick, and pray.

When they entered the yard of Carcharon it was clear that something had changed for the worse. The ground was shuddering beneath them, the drumming was loud and frantic, and showers of crimson and orange light kept bursting out of the tower windows and the air vents. She really did not want to go down there.

“Do you think this is the end?” said Wilm.

“Yes. I think it is.”

As they crept hand in hand down the yard, the tower shook; loose stones slid out of the wall and tumbled down the ridge, crashing and smashing all the way to the bottom. It had been sunny during the day and the frozen corpses of Rasper and his three assistants stood out above the melting snow like zombies in a white fog. It was a horrible omen.

“What if we’re too late?” said Wilm as they went in.

“We’ve got to keep going.”

“But the Merdrun drove the mighty Charon into extinction. What can we hope to do?”

Aviel was thinking the same thing but saying it aloud did not help. “Ordinary people have beaten great enemies before.”

Wilm’s silence was eloquent.

“Wilm?” she said, desperate for some encouragement, even the smallest.

“Malien said don’t use mancery near the stone. And scent potions are mancery.”

“What choice do we have?”

She took his cold hand in her freezing one. He seemed to take comfort from her courage – if only he knew how despairing she was – and they crept down between the juddering walls and through the cracking and crumbling passages. She was shaking and he was too. She did not want to go in; she never wanted to see Unick again. Most of all, she did not want to go anywhere near the stone. If he caught her he would feed her to it, and she was a bit corrupt now – this time it might take her.

Finally they approached the cavern. It was sweltering and the glow from the summon stone was such a lurid and penetrating crimson that it passed through the solid rock, lighting it up like glass. They turned the corner and Aviel’s knees gave.

“I… don’t think I can do it.”

Wilm held her up. “Yes, you can. You will.”

The summon stone seemed to have grown, though that might have been the baleful red corona surrounding it. The drumming, however, was oddly thick here, as if muffled.

“The time must be close,” croaked Wilm. Then he jumped. “Aviel, I can hear people talking.”

She could too, distant, echoing voices. “Lots of people… as if they’re on the other side of a wall. And one deeper voice. It sounds like he’s giving orders but I can’t make out the words.”

Wilm turned slowly to face her and in the garish light his eyes appeared to be bleeding. “Is he giving orders to an army,” he whispered, “or to the stone?”

Then one voice soared above the rest. Gergrig? Is it ready?

Almost.

“Quick, use the scent potion,” whispered Wilm.

“I can’t use it on the stone,” said Aviel. “Only on Unick. Where is he?”

“He’s here!” said Unick in a clotted voice. He stepped out from behind the stone, the Origin device swinging from what remained of his left hand.

Aviel let out a scream. All his toes were gone save for the big ones, and he had lost two fingers on his left hand, three on the right, and both ears. He was a lurching, scabrous monstrosity who should have been dead. Perhaps only willpower kept him alive, and how could she hope to master a will that strong? Surely only death could.

The floor quivered violently, tossing her off her feet. A crack formed across the middle of the cavern, opened to the width of a foot, then snapped closed, squirting dust up in a series of little grey fountains. The summon stone flared. Aviel’s innards knotted.

“Soon,” Unick said to the stone. “Very soon now.” He took a step towards her.

Wilm drew the black sword and sprang. But Unick ducked, caught Wilm’s free arm and jerked him forward so hard that he flew through the air towards the stone.

Aviel screamed.

He struck it side on and the sword was jarred out of his hand. The right side of his head hit the summon stone, there was a red flash and a puff of smoke, and the drumming became a thundering roar. Wilm hurled himself aside, gasping and clutching at his bloody ear. Where his clothing and hair had touched the summon stone he was unharmed, but the top half of his right ear was gone, taken by the stone.

He began to shake uncontrollably. He reached for the sword but his knees gave and he went down on his back. Unick had been disabled for some minutes after the stone fed, and Wilm would be too.

Aviel felt sick, and guilty. He was only here because of her, and now he was going to die. She fumbled the scent potion out of her pouch, her hands trembling so badly she could barely undo the wrappings. Unick, who was bending over Wilm, turned and stared at her, a half-smile playing across his broken mouth.

As she dropped the wrappings and took hold of the stopper, the summon stone projected a red-tinged shadow onto the end wall, though the space between the two uprights was open, not closed. Was it the other side of the gate? Was it Cinnabar?

Through the gate Aviel saw the outline of an armed host. The Crimson Gate must be opening.

Gergrig, there’s someone at the summon stone.

Gergrig, a lean man with a shaven skull and a dense black beard, brandished a recurved blade in Aviel’s direction.

“That’s a good sign!” she said in a croaky voice. “He’s afraid we can still block him.”

“Use the potion, quick!” yelled Wilm.

Unick lurched towards her, smiling sickeningly. Aviel rehearsed the compulsion she planned to use on him – Smash the stone!

She tugged on the stopper – which stuck. Curse her bad luck. As she heaved on it her right foot twisted on a patch of jellied blood, she lost her balance, and the phial flew from her hand. She dived after it, ignoring the agony in her ankle, but the phial struck the wall and smashed. He wouldn’t even get a whiff of the potion she had spent so long making.

“I’m sorry, Wilm!” she wept. “I’ve ruined everything.” She knelt, paralysed, as Unick lurched towards her.

Wilm let out a howl of anguish. “You’re not touching her!” he cried. “You’re NOT!”

He managed to crab backwards and grab the black sword. Still lying on his back, he slashed the blade straight through Unick’s left wrist. His hand went in one direction and the Origin device in the other. Aviel reached up with both hands and caught the heavy device, dropped it but caught it again.

But the figures were thickening on the other side of the shadow gate, becoming more solid. Unick, his wrist spurting blood, kicked his severed hand at the summon stone like a sacrificial offering, and it flared.

The shadow gate hardened. The army started to firm and become real. Unick staggered towards Aviel, clearly intending to feed her to the stone.

Wilm forced himself to his feet and, as Unick reached for Aviel, coldly ran him through. “That’s for Dajaes too,” he said softly.

Unick grunted, dragged himself off the blade, lurched around in a spiral and crashed face first into the summon stone.

And as it took him, he let out a dreadful screech of horror and despair. “You can’t do this to me! I opened you. I’m special —”

First it took his face, then his head, neck and body, all gushing stinking brown smoke as he was drawn in and annihilated. His legs went, his hideous feet, then with a flash of crimson he was gone, leaving nothing behind but smoke and a lingering stench, and a pair of ragged big toenails pinging off the walls.

The shadow gate became a real gate, the Merdrun real soldiers. They were about to come through. Aviel reacted without thinking, just knowing that the summon stone was like a live thing now, and live things could be poisoned. She twisted the tubes of the Origin device apart, took the heavy glass container of quicksilver from inside and hurled it at the stone. It smashed, and deadly quicksilver drenched the summon stone.

It flashed crimson, black, crimson, then a deeper, impenetrable black. The Merdrun cried out in terror. The uprights of the summon stone ground together, separated, crashed together again and the shadow gate split into two separate gates. The one with the Merdrun in it, which was a brilliant throbbing crimson now, began to spin, faster and faster until it was a red blur, then shot upwards and vanished.

The other gate, which had an azure hue, enveloped Aviel and Wilm, spun like a top, appeared to drill down through the solid rock below the cavern, and took them with it.