            Kreacher had been attempting to make her miserable. Instead, he’d given her a key to bringing "dead Master Black’ back. The potion, though...Boosted Dream Dose was highly illegal and took months to brew. Snape must have made it in case the Order wanted to torture without physically harming or using magic—given the circumstances of the war, anyone taken prisoner would likely experience garish nightmares while under the potion’s effects. In theory, the potion opened the taker’s soul into unknown dimensions, usually allowing unimaginable creatures or scenarios to run rampant. It was also highly addictive, after more than one or two doses. The taker would crave the potion even as his or her nightmares grew worse. The illegality, combined with the dangerous side effects, would keep her from taking it again.