Throughout history, humans have pondered the question of their existence. In nearly every society, part of the answer has included some form of god or goddess. For the Mayans, one such deity was Ajtzak, who tried to create humans from wood; for the Yorubas of Africa, Shango controlled the thunder and lightning. The Chinese of the Shang dynasty era worshipped Shang Ti. Evil deities were also part of the answer, as in the case of the Kuvera, the Hindu chief of evil in the Vedic period, and Tu, the Persian or Islamic demon of fatal accidents.

All of the known ancient gods, many heretofore obscure or known only from mythological literature, are included in this exhaustive reference work. The focus is on their origins, histories, and functions. The people who believed in each deity are identified, along with alternate names or spellings both old and modern. The descriptions that follow are of the functions, origins and physical nature of the deities. Extensive cross references are provided for alternate spellings and names.