"There's something wrong with those Inferi!" Harry shouted.
He hardly needed to shout. When the others saw that a little under half the gray smoke remained even after being burned by Fiendfyre, they knew something was wrong with it.
Qiu flicked her wand, sending a powerful wind toward the gray smoke-a Hurricane Charm.
Wind blew smoke away. Qiu felt she had chosen exactly the right spell for the job.
But something strange happened. The hurricane flattened the grass on the Quidditch pitch and sent Harry's robes snapping, yet it failed to move the gray smoke, which continued drifting slowly in place.
The gray smoke seemed to possess an enormous mass utterly unlike that of smoke.
"What's going on?" Qiu looked incredulous too, clearly unable to understand what was happening with the gray mist. Fiendfyre couldn't burn it away, and wind couldn't move it either?
"That's deathly aura!" Lupin spoke up then.
"It seems Voldemort's Inferi have been stored in some special way for a very long time. They've accumulated so much of the deathly aura belonging to the undead. Ordinary magic and dark magic both struggle against this kind of deathly aura, because it's magic even more corrupt than dark magic."
As he spoke, Lupin raised his wand. "Protective magic is more useful at a time like this." Platinum flames were already streaming from his wand tip as he spoke, and wherever they passed, the gray mist began to dissolve.
It wasn't particularly fast, but it was almost on par with Harry's earlier use of Fiendfyre.
Harry had understood what was happening as soon as Lupin identified it as deathly aura.
The memories he had obtained from Voldemort contained knowledge about deathly aura. Harry simply hadn't thought of it right away.
Now that he knew it was deathly aura, he