Mortaeus flower

The Mortaeus flower is a plant that grows underground on the roots of the trees in the Forest of Balor. The flower's petals are poisonous, capable of killing a human in four or five days unless altered with magical enchantments, in which case the petals can kill in as little as two days. An antidote to the poison can be brewed from the leaves of the same flower.

A mortaeus petal was used by the sorceress Nimueh in her attempt to poison the warlock Merlin with a poisoned goblet. Merlin was saved when Gaius determined the nature of the poisoning, and Prince Arthur Pendragon ventured to Balor and descended into the caves below the forest to find the flower and procure its leaves.