“Once when Hogwarts was being built,” Dumbledore said. “A monster was kept in a deep cellar.”

“Why?” asked Harry, thinking uneasily of the basilisk. They stood in front of a massive cellar door. It had been made from a single slab of cold metal. Spells and seals were scrawled over it, and bolts as big as Harry’s head studded the edges. Snape was there as well, helping with a whole mountain of scrolls and books that were needed for the spell. He rustled around on a small table behind them. Harry tried to ignore him.

“It was a cursed creature,” Dumbledore said, drawing a new seal on the door with his wand. The symbol glowed gold and then faded to white. “A Muggle had been turned into a monster by a careless curse. Our predecessors contained it here to see if it could be returned to normal.”

“Could it?”

“No...The transformation was complete. Not even the poor Muggle’s mind had survived. It killed the witch who tried to help it and was then blasted with every spell possible until there was nothing left. These walls and door are made from nullifite iron, which is naturally magic-resistant. The bars of Azkaban are made of the same metal.”

“Will it hold the Morthahg then?” Harry asked.

“It shouldn’t have to...” Dumbledore half-smiled at him over his shoulder. “If the Morthahg can be lured through the World’s Door, it can be banished back to where it came from. If not, the nullifite can hold it until we try again.” It was strange to have such a vague plan from Dumbledore. Harry wondered if it would work at all and then felt a touch of guilt for doubting.

“Where will you send the Morthahg?” he asked to cover it up. Dumbledore pointed the wand at a scroll and it unrolled to show what looked like a map drawn by an angry monkey with a calligraphy pen. Harry turned it sideways and then upside down, but it made no more sense that way.

“I can’t read it,” he admitted. He heard a soft sound from Snape, but wasn’t sure if it was contempt or amusement or both.

“Neither can I,” said Dumbledore, surprising him. “but I know what it says. This is a map, young Harry, of levels. You’ve heard the Muggle stories of seven levels of Hell?” Harry nodded. “There are many more levels than seven and not only Hell has them. The Morthahg came from here,” he went on, pointing to a spot on the map and tapping it lightly.

“What level is that?” Harry asked, pushing his glasses further up his nose.

“The Morthahg was born from fear and the hate that comes from being afraid,” Dumbledore turned back to preparing the door. “It’s a level of the mind.” That didn’t make much sense to Harry, but he nodded anyway. “Several professors have been flying out over the Forbidden Forest all night, using magic to herd the Morthahg to places where it can do the least harm. When this spell is completed, we hope to use the World’s Door in this cellar to send the creature to that level. The trick will be to lure the creature through the door alone.”

“Lure it with what?” Harry asked.

“What indeed?” Dumbledore drew a pronged spiral on the door and the shape bled into rune shapes. “And more importantly, what bait could be sacrificed? Whatever is in the room with the Morthahg will be banished with it.”

“Perhaps someone will volunteer,” Snape said icily. Harry thought the Potionsmaster was talking about him, but then followed his gaze to where Sirius had appeared down the hall.

“I know who I would nominate,” his godfather replied, just as nastily. He was dripping wet and shivering. Esme still hung from his arms. Snape sneered at that, but jumped when he saw Lorelei floating along behind him.

“What happened?”

“Family quarrel,” Sirius sighed. “Open the door for me will you, Harry?”

All three of them sprang to help. Harry ran to hold the door, Dumbledore hurried through it to inform the infirmary, and Snape took up the rear to hover over Lorelei. Sirius just hoped he wouldn’t get sick again.