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
Exotic Encounters     Pathfinder original/official source
Mythic Adventures     Pathfinder original/official source
Monster Monday (web)     D&D 5e original/official source
Monster Manual     D&D 4e (no source link)
Hacklopedia Of Beasts     Hackmaster original/official source
Monster Guide     World Of Warcraft RPG original/official source
Jorgi's Bestiary     Trudvang Chronicles original/official source