Room of Requirement.
Ian had been holding that highly suspicious piece of parchment, spying on Snape's movements. After Snape returned to his office, he merely wandered around inside and did not leave Hogwarts.
"That was obviously mine! Mine! Don't you agree?" After Snape left, Ian pulled out the Dementor again and used the creature, incapable of offering any verbal rebuttal, as someone to vent to. The utterly uninterested Dementor merely stood there like a lackey, continuously making sucking noises.
It sounded like the rattling breath of someone on the verge of death. To Ian, it sounded as though there was phlegm stuck in its throat. He had no idea whether it was trying to absorb the young wizard's emotions and soul.
"Damn Snape! He must be trying to claim my creation as his own, register a patent, open a shop, and sell it himself! I never should have said it would sell better than the Potter Family's shampoo!" Ian was indignant and unwilling to let it go. He felt that Snape had to be jealous of the talent he had inherited from Teacher Morgan.
A product as era-defining as the Unlimited Firepower Potion could clearly make anyone rich enough to establish a wealthy family. Of course, that was only if its owner could keep hold of the wealth-generating formula.
In Ian's view.
Snape's earlier threat might have stemmed from concerns that the families monopolizing various Wizarding World industries would move to persecute him. The pureblood families could not have maintained their glory for so many years without doing plenty of evil behind the scenes.
Those spoiled heirs might look like a bunch of idiots at Hogwarts, but when it came to doing things without any bottom line, they might be even more ruthless than Tom Riddle in his no-nose state.