The Secret herb is an item appearing in both EarthBound and Mother 3. When used, it cures a wide variety of status ailments and revives an incapacitated character with 50% of their health. However, the Secret Herb might also sometimes fail to work, wasting the item. After reviving someone with it, any healing done to another character also heals the revived character by the same amount. Violent Roaches drop them 1/128% of the time. 

In Earthbound

Unlike the Refreshing herb in EarthBound, it also cures paralysis, unconsciousness, and diamondization. It can be bought in Saturn Valley, Scaraba or Toto for the price of $380.

In Mother 3

This item makes a reappearance in Mother 3, serving the same purpose as the one in Earthbound. It can be dropped by an assortment of different enemies. It can also be bought at the shop in the Empire Porky Building for 600 DP.