If historical records are accurate, this potion has not been seen on the earth for at least 1,500 years. Full records of how to create this poem exist, in Snix's own handwriting, but the potion can no longer be created due to the extinction of several plants the produce vital ingredients for its creation.
This potion was purported to be used by Snix to heal sick and/or wounded children and animals encountered as it traveled the world. While many existing potions are known to cure a poison or heal wounds, this was a true "elixir of life" -- one that could be used to cure any disease, heal nearly any wound, and even aid in more acute conditions, such as paralysis, heart conditions, blindness, and other maladies. There is no complete, document list of all of its possible uses.
Creation of this potion is extremely time-consuming -- with a single potion taking as long as a week to create. The challenges of using this potion are further compounded by the speed at which it is able to heal -- with multiple potions being needed over an extended period of time (the length depending on the severity of the ailment) to be effective. Thus, it is usually necessary to have a large store of this potion on hand before it is needed, in order to properly care for an individual.
While no written evidence exists, legend tells of this potion being able to also cure magical afflictions -- although curses (vampirism, lycantrhopy, undead curses, etc) are not thought to be curable through this potion.
Marveldraught is reputed to keep for many years, or even decades, before spoiling or losing its potency.