That morning, Minerva was startled out of a rather chaotic dream. It had been Hallowe'en and for some reason the ghosts had started multiplying. The Great Hall had been crowded and several of the living students were frozen to their chairs. The pumpkin juice had solidified to orange blocks in the jugs.

But while all of that had been rather blurry, the image of Sybill, standing in the corner, arms crossed and shaking her head, had been razor-sharp. Minerva didn't need to hear the words to understand what she was saying: "I told you so". And then she had been awake, gasping and struggling with her blankets to sit up and take a sip of water. She still didn't know what had woken her up.

A look at the clock told her that it was far too early to get up, but she doubted she would be able to sleep now. With a sigh she put on her glasses and grabbed the book she had been reading right before she fell asleep last night. Apparently, some theories said that those who remained as ghosts did so because they had not yet run out of life force. This would imply that they didn't actually need the heat, but the book did not provide any kind of explanation for why ghosts did absorb heat, and Minerva soon discarded it entirely. Halfway her last chapter, everything had started to sound vague and mysterious, almost like Sybill when she was trying to pass off one of her more outlandish predictions.

Sybill who had given her such a disapproving look in the dream because she hadn't solved the problem yet.

After reading the same sentence at least three times, Minerva realised that she didn't need the Divination teacher to explain why she had had that strange dream. To be honest, she had missed how the chapter had somehow gone from describing the seven levels of life force to different ways to relocate ghosts, but the latter subject rather reminded her of that year's Hallowe'en.

The Battle of Hogwarts had cost far too many lives, but the losses had not only been on their side. In fact, about a quarter of the ghosts had been Death Eaters and those sympathising with their cause. Obviously they hadn't been welcome at the castle, but there hadn't been much the staff could do to keep them off the grounds. Ever since the start of the school year, they had been terrorising the students and even Peeves had hated the idea of having them out there.

But then, at Hallowe'en, the 'Outsiders', as the students had named the Death Eater ghosts, had taken things too far. It had started during first period, when they had been harassing a group of Hufflepuffs going down to the greenhouses to such a degree that the entire class had ended up in tears and three of the boys, in a desperate attempt to chase the ghosts away, had begun throwing rocks and smashed nearly all the glass in Greenhouse Two.

The boys were very contrite, but no one had blamed them. One of the girls, a young but talented muggleborn, had been so swarmed by ghosts that the poor girl had frostbite on both hands and cheeks. Madame Pomfrey had been livid and all but insisted that Minerva contacted the Ministry and demand that they send a team of Aurors or something. Anything to rid the school of this menace.

All outside lessons had been cancelled for the rest of that day, but the Outsiders were not done. When it was time to head down for the feast, the students had been subjected to cruel and often very personal taunts from the ghosts, crowding at every single window of the castle.

But, unbeknownst to the living inhabitants of the castle, a war council had been held that afternoon. Suddenly a roar had rung through the school and every single Hogwarts ghost, young, old and ancient, had swarmed through the Entrance Hall and out the double doors, streaming up along the castle walls, attacking the ghosts who were lurking there.

The battle had been fierce. And eagerly followed by the students, who were now struggling for room at the windows, pressing their noses to the glass to see.

It had been over much sooner than could have been expected. Led by Fred Weasley on a silvery broomstick and Sir Nicholas on a smoky steed, the Hogwarts ghosts had chased the Outsiders across the lawns, past Hagrid's cabin and into the Forbidden Forest.

At this point, Minerva had gathered all the teachers, prefects and the Head Boy and Girl, and they had rushed out onto the grounds, laying a web of charms along the edge of the forest, keeping the malevolent spirits in.

To raucous cheers, the ghosts had returned to the castle in proud formation and the feast had turned into a celebration of the victory of Dumbledore's Last Army.