Light Prognosticus
The Light Prognosticus is a book of prophecies in Super Paper Mario. Written by either Merlumina or Merloo (both are stated to have written it in-game) and created to counter the Dark Prognosticus, it tells the future in a more optimistic view. Its main role is to instruct how the universal destruction prophesied by its grim counterpart can be prevented but, as Merlon says, its main purpose was to counter the Dark Prognosticus and so it is not actually prophetic; that is to say it says what one can do but, unlike the Dark Prognosticus, it does not say what will happen.
The Light Prognosticus tells of a "legendary hero" who can stop The Void from engulfing the universe through the use of the Pure Hearts, and about the Heroes of Light. The book also tells of three other heroes who will aid in the legendary hero's quest to save creation. However, it also claims that the "man in green" will determine which Prognosticus fate becomes true.
The Light Prognosticus says that all worlds will be destroyed unless the one protected by the dark power is destroyed. It is initially thought that the dark one is Count Bleck, however, it is later revealed to be Dimentio.
The Light Prognosticus is in Merlon's possession, who studies the book to find clues in order to clarify events. From his studies he determines that Mario is the person who fits the legendary hero's physical description.