Potion, rare
Curse. Upon taking a single sip of this potion, you are afflicted with some form of madness. Roll 1d6. On a 1-3 you are afflicted with a short-term madness (DMG p. 259); on a 4-5 you are afflicted with a long-term madness (DMG p. 260); on a 6 you are afflicted with an indefinite madness.(DMG p. 260). The remainder of the elixir loses its magical properties, becoming merely a foul tasting liquid.
