Bill-E loved zombie films. He thought there was nothing cooler than corpses coming back to life and eating the brains of the living. But I don't think he'd have been thrilled if it happened to him in real life, like it's happening to us now.

The revived dead throw themselves at us slavishly, mindlessly, silently. They move as fluidly as in life, not in the shambling manner of movie zombies. Some are hampered by the loss of limbs and stumble sluggishly. But most are as quick on their feet as any living person.

They look more like living people too. They're not rotting, misshapen monsters. It's easy to rip the head off an inhuman beast from another dimension, but doing that to someone who looks human feels like murder. It's horrible.

The woman I picked off the floor tries to claw my throat open. I shove her away and turn to kick a man in the head before he bites my thigh. Ahead of me, a girl throws herself down the stairs and knocks Kirilli over. She snaps at his left hand and chews off his two smallest fingers. He screams, then sets her aflame, instinct lending him the magical fighting impulse which he previously lacked.

"Zombies!" Dervish snorts with disgust, scattering a handful with a ball of energy. "First werewolves, then demons, now zombies. What will they throw at us next?"

"There might not be a next," Sharmila says, helping Kirilli to his feet and shooting a bolt of fire up the stairs. There are shrieks from the zombies above us and the stench of burning flesh and hair fills the air. Sharmila grimaces, but sends another burst of flames after the first.

"You're not worried about this lot, are you?" Dervish says, sending more of the living corpses flying across the hold. "We can handle them. We've faced a hell of a lot stronger in our time."

"You miss the point," Sharmila replies with forced calm. "The dead are meant only to delay us. There is our true foe." She points to the centre of the hold. The ball of light is almost level with the ship. As we watch, it breaks around the hull and disintegrates. A black, hissing ball of nightmares explodes through the shield of energy and gathers around the lodestone.

We only got a glimpse of the Shadow that night in the cave. Here, in the lights of the hull, it's revealed in all its furious glory. The creature is the general shape of a giant octopus, about fifteen metres broad, ten metres tall, covered in a mass of long, countless, writhing tendrils, which whip around the lodestone, tightening and loosening as the creature saps strength from the ancient stone. A few of the living dead wander too close to the lodestone and are beheaded by some of the knifelike tentacles-the Shadow doesn't suffer fools gladly. The beast doesn't seem to have a face, but I'm sure it sees us and is focused upon us.

As I gaze with horror at the massive, pulsing creature of shadows, a fat man trailing guts hurls himself at me, gnashing his teeth. I flick him away with the wave of a hand and shuffle closer to Beranabus. He's eyeing the Shadow warily.

"It doesn't feel like a demon," I note.

"I know," he mutters.

"Can we outrun it?"

"We can try."

"The stairs are free," Sharmila calls. "But more of the dead are coming. If we are to flee, we must do so now."

"What are we waiting for?" Kirilli yells. He hasn't managed to cauterise his wound. Blood spurts from the jagged stumps where his fingers used to be.

"You think we can fight it?" Dervish asks, stepping up beside Beranabus.

"I don't know."

The window Juni escaped through blinks out of existence. That seems to decide Beranabus. "Let's test it," he grunts, moving away from the door, back towards the lodestone. "Maybe it's not as powerful as it thinks."

He unleashes a ball of bright blue magic at the Shadow. The ball strikes the creature directly and crackles around it. Its tendrils thrash wildly, then return to their almost tender caressing of the lodestone. Its body continues to throb. A high piercing sound fills the hold-I think the Shadow's laughing at us.

Sharmila bends, touches the invisible barrier where the floor should be and creates a pillar of fire. It streaks towards the lodestone, slicing through several zombies on the way. When it reaches the Shadow, Sharmila barks a command and it billows upwards, forming a curtain of flames. The Shadow's consumed, its tendrils retracting like a spider's legs shrivelling up. But when the flames die away, it emerges unharmed, oozes over the lodestone and slides towards us.

Dervish leaps through the air and chops at a thick tendril. He cuts clean through it, severing the tip. The amputated piece dissolves before it hits the floor, crumbling away to ash.

The Shadow catches Dervish with another tentacle, roughly shakes him, then flings him across the hold. Beranabus halts Dervish's flight and the spiky-haired mage drops to the floor a few metres in front of the magician, gasping with pain, his skin burnt a bright pink where the tendril touched him.

"Stuff this!" Kirilli pants, and darts up the stairs. I let him run. No point trying to make him fight if he doesn't want to. Besides, I doubt he could make much of a difference.

About a dozen walking corpses converge on me. I work a quick blinding spell, then plough through them as they mill around. I squat by Dervish as Beranabus and Sharmila engage the Shadow, and swiftly cool his burnt flesh.

"Are you OK?" I ask as he sits up, dazed.

"Three," he mutters. When I frown, he smiles sheepishly. "Sorry. I thought you asked how many fingers you were holding up."

I help him to his feet. He gulps when he looks at the Shadow, but advances to try again.

"What can I do?" I shout at Beranabus.

"Get out," he roars. "You're the one it's after."

"But I can't-"

"Go!"

Cursing, I turn and run. Before I'm even halfway to the door, I feel a whoosh of hot air on my back. Glancing over my shoulder, I see the Shadow directly behind me. It's swept past Beranabus and his Disciples, barrelling them aside. They lie sprawled on the invisible floor. They're picking themselves up, turning to help me-but too late.

The Shadow seizes me with several tentacles and lifts me high into the air. I scream, pain filling all parts of my body at once. It's like being on fire, except the agony cuts deeper than any natural flame, burning through flesh and bone, turning my blood to vapour.

I somehow hold myself together. It takes every last bit of magic that I possess, but I fight the terrible, fiery clutch of the Shadow and wildly restore blood, bones and flesh as it grips me tighter and tries to fry me again. I'm absorbing memories from the beast, mostly garbled, but what I comprehend is more terrifying than I would have considered possible.

The Shadow's surprised I'm still alive. It meant to slaughter me and absorb the freed piece of the Kah-Gash. But it's not dismayed by my resistance. The beast is much stronger than me and knows it simply has to keep applying pressure. I can last a matter of seconds, no more. Then...

Beranabus is suddenly beside me, bellowing like a madman. He slashes at the tentacles, slicing through them as easily as Dervish did. The Shadow is more of a menace than any demon I've ever faced, but it's insubstantial. It's not by nature a physical creature. It can easily and quickly replace what we destroy, but it can't harden itself against our blows.

I fall free and Beranabus drags me away. Sharmila and Dervish dart into the gap we've left and attack the Shadow with bolts of energy and fire. It makes a squealing noise and lashes at them with its tentacles. They duck and dodge the blows, punching and kicking at the tendrils.

"Go!" Beranabus gasps and tries to throw me ahead of him.

"Wait," I cry, holding on. "I know what it is."

"Tell me later," he roars. "There's no time now."

He's right. I won't have the chance to explain, not with words. But I have to let him know. He thinks he can defeat this beast, that if they keep working on the tendrils, they'll eventually chop their way through to the body. He believes they can kill it, like any other demon.

He's wrong.

I clutch his small, clean hands and use the same spell he used earlier to bypass the need for words. He gasps as I force-feed him the information. Then his eyes widen and a look of shocked desperation crosses his face.

"How?" he croaks.

"I don't know," I sob.

Sharmila screams. The Shadow has ripped one of her legs loose. It rains to the floor in a shower of bones and flesh. A few of the zombies fall on the remains with vicious delight.

Beranabus is thinking hard and fast, trying to turn this in our favour. He's always been able to outwit demons who were certain they'd got the better of him.

Even in recent years, ancient, battered, befuddled, his cunning gave him a crucial advantage. He can't believe it will fail him now, but he's never had to deal with anything like the Shadow.

The lines of his face go smooth. He half-nods and his lips twitch at the corners. My heart leaps with hope. He's seen something. He has a plan!

"Tell Kernel," he wheezes, standing straight and scattering a horde of zombies as if swatting flies. "Tell him to find me."

"You want me to send Kernel down?" I frown. "But he's not a fighter. He-"

"Just tell him to find me," Beranabus sighs, then bends and kisses my forehead. "I loved you as a child, Bec, and I love you still. I always will."

Through the brief contact, I catch a glimpse of what he's planning. It's perilous. He probably won't make it out alive. But it's the only way. Our only hope.

"Don't watch," he says, and his voice is guttural, unnatural, as his vocal cords begin to thicken and change. "I don't want you to see me like this."

He whirls away and bellows at the Shadow, an inhuman challenge. Dervish and Sharmila glance back, astonished by the ferocity of the roar. Their faces crumple when they see what Beranabus is becoming.

I back away slowly, but I can't obey Beranabus's final command. I have to look. Besides, he thought my feelings would alter if I saw him in his other form, but they won't. If you truly love someone, you don't care what they look like.

Beranabus is transforming. He outgrows his suit, which falls away from him like a banana peel. His skin splits and unravels. Bones snap out of his head, then lengthen, fresh flesh forming around them. Muscles bulge on his arms and legs, like pustulent sores. They burst, then reform, even larger than before. Tough, dark skin replaces his natural covering. Only it's not really skin-more like scales.

A tail forces its way out through the small of Beranabus's back. It grows to two metres... three... four. Spikes poke out of it, as well as several mouths full of sharp teeth and forked tongues.

I catch sight of his face. Purplish, scaly skin. Dark grey eyes, round like a fly's, utterly demonic. His mouth is three times the size of my head, filled with fangs that look more like stalactites and stalagmites than teeth. Yellowish blood streams from his nose but he takes no notice. Raising his massive arms, he pushes through the undulating nest of tentacles and hammers a fist at the Shadow, driving it back.

"What the hell is that?" Dervish croaks, backing up beside me, helping the one-legged Sharmila along.

"Beranabus," I answer quietly. "The Bran we never saw. The demon side that he kept shackled. This is what he would have looked like if he'd let his father's genes run free, if he'd chosen the way of the Demonata."

Beranabus lashes the Shadow with his tail. The spikes rip through the shadowy wisps of its body, the teeth snapping at it, tearing open holes. The Shadow shrieks angrily but the holes quickly close and the beast fights without pause, smothering Beranabus with its tentacles.

Dervish, Sharmila and I are by the doorway. We should take advantage of the situation and race up the stairs. But we're mesmerised. We can't flee without knowing the outcome. Sharmila clears the stairs of zombies, to keep the route out of the hold open, but she doesn't take her eyes off the battling pair.

"Can he control himself like that?" she asks quietly as the behemoths wrestle.

"Not for long," I whisper. "This is the first time he's completely unchained his beastly half. If he maintains that shape and lets the monster run free too long, it will take over."

"How much time does he have?" Dervish asks.

"He doesn't know. He's not even sure he can turn back again. Maybe he's given it too much freedom. The Beranabus we knew could be gone forever. He might turn against us and work with the Shadow to destroy mankind."

Dervish and Sharmila stare at me as if I'm the one who's changed shape.

"Why would he take such a risk?" Sharmila gasps.

"He had to. I'll explain later. If we survive."

The beast that was Beranabus shrugs free of the Shadow's tentacles and staggers away. For an awful moment I think that he's about to attack us. But then he bellows at the Shadow and darts past it, making for the lodestone.

"Ah!" Sharmila exclaims with sudden hope. "If he breaks the stone..."

"...the Shadow will be sucked back to its own universe," I finish.

"We hope," Dervish adds gloomily.

Finding its path to me unexpectedly clear, the Shadow lunges forward, eager to finish me off. Then it pauses. It doesn't glance back-as I noted earlier, it doesn't have a face-but it's somehow analysing Beranabus. There's a brief moment of consideration-can it kill me and steal the power of the Kah-Gash before Beranabus breaks the stone?

The Shadow decides the odds are against it and reverses direction, launching itself at the transformed magician. It catches him just before he reaches the lodestone. The pair spin past. Beranabus roars with frustration as he shoots beyond his target. The Shadow whips him with its tentacles. Deep cuts open across his arms and legs, and many of the protective scales on his chest and back shatter under the force of the blows.

Just before they fly out of striking distance of the lodestone, Beranabus's tail twitches. The tip catches a notch in the stone and Beranabus jerks to a halt. The Shadow loses its grip and ends up in a heap. It's back on its tentacles within seconds but Beranabus has already jerked himself within reach of the lodestone.

He grabs the stone with his massive hands and exerts great pressure, trying to snap it in half. There's a cracking sound and a split forms in the uppermost tip of the rock. But then it holds and although Beranabus strains harder, it doesn't divide any further.

The Shadow hurls itself at Beranabus and lands on his back. Tendrils jab at him from all directions, destroying his scaly armour, penetrating the flesh beneath. One of his grey eyes pops. Several of his fangs are ripped from his jaw. Blood flies from him in jets and fountains.

Beranabus howls with agony, but otherwise ignores the assault and focuses on the lodestone. He's still trying to tear it in two. The stone is pulsing. The split at the top increases a few centimetres. The gap's just wide enough for Beranabus to jam his unnaturally large fingers into it. Snapping at the Shadow with the remains of his fangs, he transfers his grip to the crack, gets the tips of all his fingers inside and tugs.

There's a creaking sound, then a snapping noise, and the stone splits down the middle to about a third of the way from the top. Beranabus yells with triumph, wraps both arms around the severed chunk of rock and rips it free of the lodestone, tossing it to the floor as an oversized ball of waste.

The Shadow screeches and scuttles after the rock, perhaps hoping to reattach it. I quickly unleash my power and send the piece of stone shooting across the hold. It smashes into the side of the ship and explodes in a cascade of pebbly splinters.

Beranabus roars with ghastly, demonic laughter and bites into one of the Shadow's tentacles. As he rips it off, another tendril strikes the side of his head and slices through to his brain. The triumph that had blossomed within me vanishes instantly.

"Bran!" I scream and dart towards him. Dervish holds me back.

The Shadow strikes repeatedly at Beranabus in a tempestuous rage. It gouges great chunks of flesh from his chest and stomach. Scraps of lung, slivers of a heart and other internal organs splatter the broken lodestone. Then, in a childish sulk, the Shadow tosses him aside like an old doll it's finished playing with.

The demonic beast that Beranabus has become rolls over several times before coming to a rest near the side of the hull. Again I try to race to his aid, but Dervish has a firm hold and doesn't let go even when I bite him.

Beranabus raises his huge, transformed, scaly head. He glances at the Shadow and the lodestone with his one bulbous grey eye and grins. Then his head swivels and he looks for me. When he finds me struggling with Dervish, his grin softens and I see a trace of the Beranabus I knew in the expression. I also see the boy he once was-scatterbrained Bran. He smiles at me foolishly, the way Bran used to, and gurgles something. I think he's trying to say, "Flower."

Then the grey light in his eye dims and extinguishes. The smile turns into a tired sneer. He coughs up yellow blood and tries to drag himself forward. But the strength drains from his arms. His body sags. A jagged breath dances from his lips and his head drops. By the time his forehead connects with the cold steel floor of the hold, the three thousand year old legend is part of this world no more.