"Therewith the slayer of Argos gave me the plant that he had plucked from the ground, and he showed me the growth thereof. It was black at the root, but the flower was like to milk. Moly the gods call it, but it is hard for mortal men to dig; howbeit with the gods all things are possible." -- Odyssey, Book X.
A herb which can resist sorceries. It was given by Hermes to Odysseus when the latter was stranded on the Isle of Aea and half his men were turned into swine by Circe. Odysseus had to consume the herb to be able to face Circe and force her to undo her sorceries.