The Dark Prognosticus is the opposite of the Light Prognosticus. It is a book containing powerful, dark prophecies. Count Bleck uses it to destroy all worlds. It created "The Void," a giant hole in the sky. It became too large in World 6 (Sammer's Kingdom) and destroyed it, creating the World Of Nothing , a formless, white space in which nothing happens, except a battle of Mr. L , who will battle you in his giant "Brobot 2.0". The DP Is the main part of the storyline in Super Paper Mario.
Another allusion to the fact that Dimentio himself may have written the book is that Count Bleck did not originally want Dimentio as his minion. However, the book's prophecy mentioned a being of Dimentio's description, so Bleck took him in. The Dark Prognosticus also states Luigi (simply called the "man in green") is the perfect host for the Chaos Heart.