Hogwarts: I'm Truly a Model Wizard

After about ten minutes, the two Dementors finally left after inspecting all the train cars, and the lights in the aisles and on the shelves flickered back on. The dim light seemed to chase away the lingering cold, and as the surroundings brightened, voices gradually started up again on the train.

"What was that just now..." Kanna asked, still shaken.

"Dementors," Kyle replied, placing the luggage back on the shelf. "Guards of Azkaban."

"I know what a Dementor is," Kanna said, shaking her head. "I meant the Charm you just used to dispel the cold."

"Oh, that..." Kyle handed out some more chocolate. "The Patronus Charm. It's the easiest and most effective way to ward off Dementors. If you can summon a full Patronus, it can even drive them back."

"Huh? Didn't you just use the Wand-Lighting Charm?" Fred asked from beside her, surprised. He'd only seen Kyle pull out his wand and then the compartment had lit up. Wasn't that just the Lighting Charm?

Kyle didn't answer him directly. Although the Wand-Lighting Charm and the Patronus Charm both produced light, they were, in reality, very different—though admittedly, if you didn't look closely, they might seem similar.

"A full Patronus?" Kanna asked, curious. "What does it look like?"

"The light forms into a silvery-white animal," Kyle explained. "It can run and jump freely in midair, almost as if it were alive."

"Is it difficult to do?" Kanna asked, wondering. She hadn't seen any animal appear in the compartment earlier. While she was eager to learn the Charm, if even Kyle couldn't summon a full Patronus, it might not be worth the effort.

"It's challenging, but not impossible," Kyle said. "If you have a particularly strong, happy memory, it becomes much easier to cast."