The finest - and most expensive - whisky available in Ankh-Morpork. Bottled by Jimkin Bearhugger's Whiskey Distillery, even a sniff of it is like Hogswatch. Sir Samuel Vimes once had to empty an entire bottle onto his carpet to foil an elaborate set-up. This, even more than the attempted entrapment, was enough to make him determined to catch the perpetrators.
The prefix "Mac-" is attached to some of the finest Scotch single malt whiskies available. Examples include Macallan and MacPhail; some use the definite article (e.g. "The MacAllan"). Although there are far more decent whiskeys prefixed with Glen- or La-, Mac is authentically whiskyish, being definitively Scottish. The added twist (whisky with a twist? Behave!) is that the word Macabre means "Suggesting the horror of death and decay; gruesome".