The potion of cure is a useful situational potion. Lysis will make one if she has a rat tail and a potion of extra life. The potion is the easiest way to get rid of disease and poison, aside from dying. Consuming the potion will instantly remove disease, but with bad luck it can be caught again right away. A drinking level of 10 is required to guarantee success.
Lysis buys potions of cure for 39 gold and sells them for 150. Darklow buys them for ? gold.