"You've found Thaumatagoria! I always thought it was a myth! A story told to excite potion-makers, to make them dream impossible dreams! The rumours about its properties are legendary, you wonderful, wonderful young potioneer!"
-- Zygmunt Budge (BoP)
Thaumatagoria is a rare magical plant used by Potioneer Zygmunt Budge in the Potion of All Potential.
Confirmed from Book of Potions Game Files by Harry Potter Wiki