Dracopedia Bestiary: An Artist's Guide     Any original/official source
The Monsters Know What They're Doing     Dungeons And Dragons original/official source
Angry Golem (web)     D&D 5e original/official source
Pathfinder 1e Bestiary 1     Pathfinder original/official source
Pathfinder 2e Bestiary 1     Pathfinder original/official source
Mythic Monster Manual v1     Pathfinder original/official source
Mythical Monsters Revisted     Pathfinder (no source link)
Exotic Encounters     Pathfinder original/official source
Monster Manual     D&D 5e original/official source
Flee, Mortals     D&D 5e (no source link)
Creatures Of Vathis     D&D 5e original/official source
Monster Ecology Anthology     D&D 5e (no source link)
Monster Manual 3     D&D 4e (no source link)
Dragon Magazine Monster Ecologies     D&D 2e/3e (no source link)
QUERP Bestiary     QUERP 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