The Monsters Know What They're Doing     Dungeons And Dragons original/official source
Angry Golem (web)     D&D 5e 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
Mythic Adventures     Pathfinder original/official source
Monster Manual     D&D 5e original/official source
Monster Ecology Anthology     D&D 5e (no source link)
Monster Manual 2     D&D 4e (no source link)
MojoBob (web)     D&D 2e original/official source
D&D 2e Monstrous Manual     D&D 2e original/official source
Scruffy Grognard's Monstrous Manual     D&D 2e (no source link)
AD&D Monster Manual     AD&D 1e (no source link)
Dragonlance Bestiary     SAGA (no source link)
Hacklopedia Of Beasts     Hackmaster original/official source
QUERP Bestiary     QUERP original/official source
Monsters: A field Guide     HARP (no source link)
The Monster Overhaul     OSR (no source link)
Creatures Of Barsaive     Earthdawn original/official source
Lairs And Encounters     Adventurer, Conqueror, King (no source link)
Baby Bestiary 1     Any original/official source