From the introduction:
This [product] contains thirty monsters from the World of Tarrak, ready to enter your fantasy world.
Presented in the Popular Compendium Format.
The first printing was titled "Fantasy Monsters", later printings were titled "Tarrakian Monsters". The product otherwise was identical, even using the same product code. While advertised as compatible with "any fantasy roleplaying game", the format and content was squarely aimed at Advanced Dungeons & Dragons, 2nd Edition.