Cockatrice

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