Ghlen Livid
Ghlen Livid is a wine made from the freeze distilled Vul Nut, a reannual plant. Reannuals travel back in time, so Ghlen Livid can give it's drinkers a vision of the future, which is, from the nut's point of view, the past. It has a distinctive green colour and brewed in the Rehugreed province of the Agatean Empire and is first seen in The Colour of Magic. This temporal anomaly is why Pteppic did his Final Run under the added handicap of a hangunder.
Annotation
A reference to Roundworld's The Glenlivet. According to empirical tests the Roundworld version doesn't show any useful visionary effects. But it is rumoured that extensive tests are going on nevertheless.