"Oh, my Potions—"
Mia climbed up from the floor and saw how badly the floor had been corroded by her Nurgle soup. She felt a little regretful. She had brewed that Potions herself, and now it had all spilled out. It was hard not to feel heartbroken.
"Scourgify—Scourgify—"
Roy was dealing with the puddle of green soup on the floor. He had no idea how Mia had invented such a lethal liquid. This green stuff was not only highly poisonous, but absurdly corrosive as well.
Even more outrageously, the green liquid was actually resistant to spells. Roy's Scourgify seemed completely useless against that puddle of vomit-like sludge.
Seeing that the puddle of pus was about to burn straight through the floor, Roy had no choice but to use the Sealing Charm. He sealed the constantly boiling, writhing sludge into a magical container he had prepared beforehand for separating the Obscurus.
After Roy cleaned up the mess Mia had created, the siblings finally noticed that a huge hole had already been burned through the floor of their room.
"Ah, what a shame about the floor."
"Ah, what a shame about my Potions."
Meanwhile, in Snape's office beneath Hogwarts.
Snape had also sealed the puddle of green pus Mia had created into a specially made glass vessel. As he watched the viscous sludge constantly churn and boil inside the custom hourglass-shaped container, even Snape, who had studied Potions for half his life, wore an expression of shock he had never shown before.
"How is this possible?"
Snape stared at the sludge in the glass vessel, which wriggled as though it were alive. His usually calm eyes were filled with shock and unease.
"Is this the effect of the Obscurus?"
Snape rested both hands on the table before him, deep in thought