The appearance of the herb is mostly unknown, just that it is a bright shade of green.
Lyssop is a rare herb that grows in the Southern Kingdoms. It used to grow in Ambala, but the population there died out a few hundred years ago. It has been known to be found in the Forest of Tyto, but in what quantity is unknown. The herb appears exclusively in A Guide Book to the Great Tree.
When the Great Tree was infested with Blackfire Mushrooms, the Ga'Hoolology ryb Isolde sent out members of her chaw to investigate a cure. Pollianne and Hildeth were sent to Aude, a tree healer in the Shadow Forest who knew that the only known way to heal black fire was with a concoction made from Lyssop. The chaw then goes to the Dark Sisters in the Forest of Tyto, where they are given a bright green potion made from the herb. They are instructed to keep the roots moist with the liquid for two weeks, and the affliction will disappear. When applied, the fiery streaks caused by the mushrooms begin to fade, turning an ashy grey. Next, the Blackfire Mushrooms die. Finally, where the streaks once were, all that would be left are empty, hollow channels.