The sinister chest, located in the Yanille Agility dungeon, always rewards nine herbs when opened: three grimy ranarr, two grimy harralander, and one each of grimy torstol, grimy irit, grimy avantoe and grimy kwuarm. Opening the chest requires a sinister key, and the key is used up when the chest is opened. Depending on the price difference between the keys and the herbs, it can be very profitable to buy sinister keys, open the chest, and sell the resulting herbs. The price of sinister keys jumps around a lot, but it's not uncommon to buy them instantly for far below the market price.