Covering large amounts of the forest floor, this poisonous plant is quite common in lowland scotland but I've never found it in Ireland.
It's quite a non discript little plant with a rather unpleasant smell. Though poisonous the poisons can be negated with heat or by drying and it has been used in herbal preparations, though to be honest I'd avoid it.
You can get a blue or yellow dye from the plant depending on the mordant you use and lore has it that the sap was blessed by the god mercury and that it glistens a shimmering silver if extracted in moonlight.