Magnus merely raised an eyebrow. “Henry,” he said. “Before he went to Idris, he sent me a vial of dirt to analyze. Said he couldn’t make head or tail of it. He also said you gave it to him.”

James had nearly forgotten that Magnus and Henry were good friends and had, famously, invented the magic that powered Portals together. “And?” he said cautiously.

“It’s strange stuff,” Magnus said. “In fact, it isn’t from this world.”

They had reached the bottom of Great Tower Street and were nearing the Tower of London. Flags waved from the turrets of the White Tower, backlit dimly against the last fitful gleams of the setting sun. Magnus nimbly avoided a group of tourists with box cameras and steered James down Tower Hill, a hand on his shoulder.

James lowered his voice, though the others were a distance away. Matthew, who was carrying the Pyxis, had stopped to point out something about the Tower to Cordelia. “What do you mean?”

“You know that there are other realms,” said Magnus. “Other worlds than this.”

Think of the universe then as like a honeycomb, each of its chambers a different realm. So some chambers lie next to one another. “Demons come from them, yes. They travel through the dimensions to reach our world and others.”

Magnus nodded. “There are some worlds ruled by demons, usually Greater Demons. Those worlds can be imbued with the very essence of those creatures. The dirt you gave Henry comes from one such place. A dimension under the power of the demon Belphegor.”

“Belphegor?” The name was immediately familiar. “He’s one of the Princes of Hell, isn’t he?”

“I know what you’re thinking about,” said Magnus, tapping his walking stick against the cobblestones. “Jem also contacted me about you. All roads lead to James Herondale these days, it seems.”

James rubbed his cold hands together. The wind off the river was sharp. “Jem contacted you?”

“About your grandfather,” said Magnus. “He told me that he was a Prince of Hell.” He glanced at the darkening sky. “You are wondering now if it might be Belphegor because the realm that you visit belongs to him.”

“Wouldn’t that make a kind of sense?” said James.

“It might. It might mean nothing at all. I can tell you that there is no record of anyone sighting Belphegor in more than a century.” Magnus hesitated. “Jem told me you were desperate to know who your grandfather is. My own father is a Prince of Hell. They are dark angels, James. Intelligent and cunning and manipulative. They bear the knowledge of thousands of years of life. Like angels, they have seen the face of the divine, but they turned away from it. They have chosen darkness, and that choice has reverberated through eternity. They cannot be killed, only wounded, and no good can come from knowing a Prince of Hell. They can never cause you anything but sorrow.”

“But wouldn’t it be better for me to know—”

“I summoned my father once. It was the worst mistake of my life. James, you are not defined by this—by this blood in you. I have found no trace, no hint of who your grandfather is, and I advised Jem to cease looking. It does not matter. You are who you are, made by the sum of your choices and actions. Not a teaspoon of demon’s blood.”

“So you don’t think it’s Belphegor?” said James. “What about Sammael?”

Magnus snorted. “Good Lord, you are determined. I recall seeking a demon for your father, once. He was equally stubborn.” He pointed with his walking stick. “Look. Here we are.”

They were in front of the bridge; though it was quite dark now and the gas lamps were lit, there was still a good amount of traffic—even the occasional motorcar purring along Tower Bridge Approach.

The others had begun to gather around. Reluctantly, James dropped the topic of his grandfather. “So, do you think you can do it?” he asked Magnus. “Create a distraction? Or should we come back later, when there are fewer mundanes about?”

Magnus’s eyes glittered. “No need for that,” he said. He stepped to the railing along the river’s edge, where a high wall dropped down to a stony beach that ran beside and below the bridge. With a flourish, he drew off his gloves and tucked them into his waistcoat pocket. Then he held out his hands. Blue fire sparked at his fingertips.

Light arced over the Thames. Bright as a thousand naphtha beacons, it formed a glimmering path laid from bank to bank of the Thames. James heard Cordelia gasp in wonder as the light rose and twined, forming the ghostly shape of a shimmering Tower Bridge made of light. It was perfect down to the last detail, from the towers to the spiderweb cables and gleaming chains.

Magnus lowered his hands. He was breathing hard.

“It’s spectacular,” said Thomas, and there was a look of real wonder on his face that James was glad to see. “But—”

“It will not appear to mundanes as it does to you,” said Magnus. “They will not see the real bridge. They will see this instead. Look.”

He indicated an oncoming hansom cab with a wave of his hand. The small group of Shadowhunters gaped as it swung toward the glimmering illusion of Tower Bridge and onto the bridge deck. The wheels of the hansom rattled over the glimmering tarmac.

“Oh, good, I was afraid the bridge was going to collapse,” said Lucie, as more carriages followed the cab.

Magnus seemed to have thrown up a glamour over the entrance to the real bridge, as all the traffic, pedestrian and even omnibuses, seemed to be swerving unconsciously toward Magnus’s secondary, shining structure.

“Magnus would never create a bridge that would collapse,” said Matthew. His green eyes were shining, and James felt a rush of affection for his parabatai; Matthew had always loved magic. It was probably why he seemed so at home in the Hell Ruelle and places like it, surrounded by enchanted fire and starry-eyed warlocks.

“Thank you,” said Magnus dryly. “If you’re going to capture that demon, you’d better get to it. I can only keep this illusion going for so long.”

James inclined his head. “Thank you.”

Magnus just shook his head slightly. “Good luck. Don’t get killed.”

James had already turned and was making his way through the archway that led to the steps up to the bridge, the others close behind and around him. All of them held seraph blades except Cordelia; as always, Cortana glimmered in her hand.

James had thought there seemed a sort of shadow hanging over the bridge, a darkness that he had attributed to the shadow of the glamour Magnus had cast. But as they gained the top of the steps, seraph blades drawn, the world began to darken in front of James’s eyes. The gas lamps flickered wildly and went out.

The stone towers cracked and blackened, deep jagged lines spreading across the pavement beneath them. The wind picked up, and the heavy steel suspension chains seemed to sway: the clouds overhead roiled and darkened in the dark gray sky. There was an acid tang to the air, as if a storm was oncoming.

“Jamie.” Matthew was still beside him; as James turned to look at his parabatai, he realized that Matthew’s hair looked white, like an old man’s. The color was leaching out of everything, turning the world to a photograph. He sucked in a breath. “Are you all right? You look—”

“I can see the shadow realm.” James’s own voice sounded hollow to him, distant and echoing. “It’s all around me, Math. The bridge is splintering—”

Matthew’s hand clasped his arm. His fingers seemed the only warm thing in a world made of ice and ashes. “There’s nothing wrong with the bridge. Everything’s all right, Jamie.”

James wasn’t sure that was true. The bridge looked warped and broken. From the cracks in the granite poured a reddish light. The blood-colored light from his vision.

The others were fanning out, looking up and down the bridge. Clouds were scudding back and forth above the bridge like anxious messengers.

James tipped his head back. More clouds were gathering directly overhead. They were heavy and reddish, almost wet-looking, as if they were filled with blood. James narrowed his eyes. He had thought he could see stars through the clouds, a few faint stars hovering above the bridge’s upper walkways. They were not stars, he realized, instinctively sliding a throwing knife from the scabbard at his waist. Stars did not have pupils, or scarlet irises. Stars did not blink.

James drew his arm back and flung the blade.

* * *

It came screaming out of the air like a diving hawk—a demon the size of an omnibus, its yellowish coat streaked with dried blood. It shot straight for James, a blur of black teeth and red talons—and a haft of gold, where the hilt of James’s knife protruded from its shoulder.

James stood upright on the bridge, his right arm outstretched, and flung a second blade. The demon ducked out of the path of the knife and landed on the bridge, taloned feet splayed. It began to move toward the Nephilim.

Cordelia raised Cortana, its golden blade slicing the air. All around her she could hear voices as angel blades were named and blazed up in light: “Eleleth!” “Adamiel!” “Jophiel!”

The demon bared its teeth as seraph light illuminated the bridge. Cordelia could see it more clearly now: the body of a mangy lion with elongated legs, each one ending in a massive, taloned paw. Its head was snakelike and scaled, with glittering red eyes and a triple row of serrated jaws. Its scorpion’s tail lashed back and forth as it paced toward James, a low growl coming from its throat.

By the Angel, Cordelia thought. We were right. It is a Mandikhor.

James caught up a seraph blade as the demon paced toward them. “Raguel!”

The blade flared up as the demon lunged, teeth bared. James flung himself sideways, avoiding its slashing claws. Matthew dropped the Pyxis and ran forward to flank James, seraph blade flashing. The tip sliced across the demon’s shoulder as it leaped back, causing it to howl. It reared up, and Cordelia heard Lucie cry out as the demon seemed to tremble all over. A grotesque lump swelled under the skin of its side—swelled and swelled and then burst into a sticky black thing. Cordelia tried not to gag as the thing peeled away from the Mandikhor, dropping to the ground. As it rose to its feet, Cordelia recognized it as one of the creatures that had attacked them in Regent’s Park. A Khora demon.