Mageroyal is an herb that can be gathered by herbalists, or bought in limited quantities from selected vendors. It requires an herbalism skill of at least 50 to gather. Mageroyal seems to be edible, as it is used in the recipe for [Delicious Chocolate Cake]. It is also mentioned in The Worst Mage in Dalaran - A Children's Book, where it is described as "glistening". The last paragraph of this work would seem to imply that mageroyal grows where magical activity has recently occurred, though obviously in the game it spawns in preset nodes.