Hellebore Root

A toxic root which is used in ceremonies of worshiping the god of the Underworld. The drug deadens the senses, described as "opening the gates to the Underworld". A sufficiently high dose will kill, described as "opening the gates too wide" (although it is not widely used as an assassin's drug). The drug clearly has a physical, pharmaceutical effect but also has a spiritual one as use of hellebore root can open the boundaries between worlds and allow Shades and living beings to cross the veil between Gaia and the Underworld.
Hellebore root looks like a typical gnarled piece of root, dirty brown on the outside. But when broken or cut, the interior reveals the five colors of the god of the Underworld, striated in a rainbow pattern. The root can be verified by rubbing it on ones skin - it causes a localized anaesthetic effect. Priests of the god of the Underworld are able to prepare the root, but the experts are the priestesses goddess of the Harvest.