Vampyr Leaf

The Vampyr Leaf became highly valued after a elven family discovered it by chance whilst adventuring through the the Tenga Va'Lu Jungles.
A curse, kept locked away in tombs of cold iron to prevent the curse spreading and blighting the flora of the jungle. This curse was created by an Iron Fey, these creatures have a deep hatred for nature.
The curse was cast to destroy the green life of Colossus but they were foiled and the curse put away. A group calling themselves the Whistling Blades. None ever managed to leave the jungles. 
The elven adventurers, The Golden Watchers, like many before were overwhelmed with curiosity and entered the cold iron tombs. Finding a magical whistle they blew it thinking it part of the puzzle to the treasure.
Instead it opened the tombs and the curse became free. The Golden Watchers had their minds pierced by the pitch of the whistle, their spirits left to wander the cold iron tombs.
Flora across Colossus fought it off but there are some that still become effected during sprouting. Having a form of albinism.
The plants cannot photosynthesise and so feed on the sugars created by the neighbouring plants.
A minotaur alchemist called Wesley was the first to create a potion from the flora that was being referred to as Vampyr Leaf. This potion became a substitute for the feeding Vampires require.
It is incredibly expensive and sort after, at least by those of a vampiric nature.
Taking the potion means they are sustained for a full cycle of the Sun. Luckily for them even a small amount of Vampyr Leaf can make a lot of Potion.
Other uses for it are being experimented with but for now the Vampires of Colossus are keen to hold the monopoly on it