Wyvern

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

Exotic Encounters     Pathfinder original/official source

Mythic Adventures     Pathfinder original/official source

Monster Manual     D&D 5e original/official source

Flee, Mortals     D&D 5e (no source link)

Monster Monday (web)     D&D 5e original/official source

Monster Ecology Anthology     D&D 5e (no source link)

Monster Manual     D&D 4e (no source link)

MojoBob (web)     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

Critters, Creatures, & Denizens     Dungeon Crawl Classics (no source link)

Monsters Compendium     Heroes Of Adventure (no source link)

Manual Of Monsters     World Of Warcraft RPG original/official source

Godforsaken     Cypher System (no source link)

QUERP Bestiary     QUERP original/official source

Mystara Adversary Compendium I     Dragon Age original/official source

Creatures Of Barsaive     Earthdawn original/official source

Lairs And Encounters     Adventurer, Conqueror, King (no source link)

Baby Bestiary 1     Any original/official source