Spontaneous generation, the idea that life can arise from non-living matter, is one of several obsolete biological concepts that can be used in fantasy games to provide a storyteller with more options for monster and setting design. There are at least three forms of spontaneous generation, Happenstance, Alchemy, and Divine Intervention, and these are all covered in this mini-sourcebook.

“Spontaneous Generation Monsters” includes guidelines on how to create, use, and incorporate into games the title sorts of creatures; descriptions of the three distinct sorts of spontaneous generation; and 17 sample monsters, two of which include variants.

Material in this publication was written specifically for the "Basic" version of the OGL/d20 system and can be used as-is or easily adapted for other games using the same core rules. It was written by noted game developer Derek Holland and includes illustrations by artist Andy Hopp.