The Monsters Know What They're Doing     Dungeons And Dragons original/official source
Atlas Animalia     Any original/official source
OSE Encounter Activity Tables     Any original/official source
Pathfinder 1e Bestiary 1     Pathfinder original/official source
Pathfinder 2e Bestiary 1     Pathfinder original/official source
Mythical Monsters Revisted     Pathfinder (no source link)
Mythic Adventures     Pathfinder original/official source
Monster Manual     D&D 5e original/official source
Monster Monday (web)     D&D 5e original/official source
Monster Ecology Anthology     D&D 5e (no source link)
Monster Manual     D&D 4e (no source link)
Monster Manual 2     D&D 4e (no source link)
Dungeons And Dragons Essentials: Monster Vault     D&D 4e (no source link)
Dragon Magazine     D&D 2e/3e (no source link)
Scruffy Grognard's Monstrous Manual     D&D 2e (no source link)
Dragonlance Bestiary     SAGA (no source link)
Hacklopedia Of Beasts     Hackmaster original/official source
Monsters Compendium     Heroes Of Adventure (no source link)
Godforsaken     Cypher System (no source link)
QUERP Bestiary     QUERP original/official source
Beyond The Black Sea Bestiary     Beyond The Black Sea (Dark Stars) original/official source
The Monster Overhaul     OSR (no source link)
Lairs And Encounters     Adventurer, Conqueror, King (no source link)
Baby Bestiary 2     Any original/official source