This item is used in the quest Garden of Tranquillity. You use it with some Rune dust to make a strengthened plant cure for the Burthorpe Vines. To make rune dust, you must use either Rune essence or Pure essence on a chisel, resulting in Rune shards. Afterwards use a Pestle and mortar on it. After the quest you can make as much as you want, but it has no use.