Killed on Sight, Executed upon Capture

"What, the smell of blood?" Slughorn looked thoughtfully at the scarlet liquid on the wall. With a light wave of his Wand, the fabricated bloodstains vanished. "I certainly hadn't considered things that thoroughly, but it was too late. I had only just arranged this place when you entered the house."

As he spoke, Slughorn let out a heavy sigh.

But soon, Slughorn turned an inquisitive gaze on Harry and asked curiously, "I would very much like to know how you, a student who grew up in Hogwarts Castle rather than a battle-hardened Auror, managed to spot these problems so quickly."

At that, Harry scratched his hair sheepishly.

He glanced at Dumbledore beside him. After Dumbledore showed his approval and gave a slight nod, Harry honestly said, "It was Linley's Illusion Formation. In the 'high-difficulty' Illusion Trials, we often have to complete different tasks under all kinds of conditions."

"In one high-difficulty Illusion Trial, I played the role of an Auror, and my task was to investigate one hundred murder cases. In many of those investigations, houses that appeared to be murder scenes were actually fabricated by Dark wizards. The fake blood was not human blood, but Dragon Blood or the blood of other magical creatures. Its bloody smell differed from that of human blood."

"Because I overlooked that and failed to notice the abnormality in the smell, I died dozens of times in the illusion. Those dozens of deaths made me more cautious and allowed me to discover the unusual smell at the fabricated scenes. It was precisely because of my experience in the illusion that, after smelling the blood here, I could tell it was not human blood. If I'm not mistaken, this should be Dragon Blood, right?"

That was what Harry said.

Slughorn said in amazement, "An Illusion