Room of Requirement

"First, Hermione, before we begin the brewing, let me take some time to explain the basic principles of alchemy to you." Tierra led Hermione toward the eighth floor of Hogwarts Castle. "We can talk as we walk."

"Okay, okay." Hermione nodded eagerly. "But aren't we going to see Professor Horace Slughorn? Why are we going upstairs?"

"The Philosopher's Stone won't be brewed in Professor Slughorn's Potions Classroom." Tierra patiently explained, "There's too little space there, too many people coming and going, and the basement is too close to Hogwarts' foundations. If anything goes wrong during the experiment or brewing process—an explosion, for instance—it could easily cause enormous casualties and property damage."

"Then where are we going?" Hermione asked.

"Dumbledore's office." Tierra said jokingly. "Let dead Dumbledore die, not Tierra."

"What?" Hermione's mouth fell open in shock.

"Hahahahaha." Tierra chuckled. "Just kidding. We're brewing it in the Room of Requirement. Brewing a Philosopher's Stone requires approximately five hundred and seventy-nine different glass and crystal instruments, three hundred and seventy-seven magical ingredients, seventy kinds of metal materials and tools, as well as thirty-five alchemical arrays."

"Even with the abilities of my Divine Dimension, brewing a Philosopher's Stone from scratch only reduces the required glass and crystal instruments to one hundred and seventy-seven kinds, and the metal materials and tools to twenty-three kinds. But customizing, purchasing, and drawing the remaining glass and metal instruments, as well as the thirty-five alchemical arrays, would still take at least three months."

"But with the Room of Requirement, it's different." Tierra explained. "It can produce virtually all the remaining glass and metal tools we need, and the bases and magical patterns for the thirty-five alchemical arrays can also be created directly inside it. That will save us at least two months of preparation time."

"Mm." Hermione nodded.