Monstrosities     Swords & Wizardry original/official source
Angry Golem (web)     D&D 5e original/official source
OSE Encounter Activity Tables     Any (no source link)
Pathfinder 2e Bestiary 2     Pathfinder (no source link)
D&D 2e Monstrous Manual     D&D 2e (no source link)
Hacklopedia Of Beasts     Hackmaster (no source link)
Critters, Creatures, & Denizens     Dungeon Crawl Classics (no source link)
Harnmaster 5e     Harnmaster (no source link)
Lairs And Encounters     Adventurer, Conqueror, King (no source link)