From the back of the book:
A mad mage | A defiled crypt | A cosmic fungal entity
They say Ursodiol the Mad was the greatest mind to have ever breached the great Cosmic Void; that he looked beyond the myriad stars and the blackest depths of the hells into the swirling magical protoplasmic morass that is the beginning and end of everything. When they found his corpse, so hideously changed was it that it drove those who saw it to madness and despair. Fearful, they entombed him in the crypt of his forbears and sealed it tight. But little did they know that Ursodiol brought back something with him from his cosmic journey. And it is hungry...
Ominous Crypt of the Blood Moss is an old-school style adventure primarily designed for use with Old-School Essentials and other iterations of the Basic/Expert rules for the original fantasy roleplaying game.
A dungeon crawling adventure of cosmic horror for characters of 2nd to 4th level!