Gnoll

The Monsters Know What They're Doing     Dungeons And Dragons original/official source

The Monsters Know What They're Doing 2 (moar)     Dungeons And Dragons (no source link)

OSE Encounter Activity Tables     Any original/official source

Pathfinder 1e Bestiary 1     Pathfinder original/official source

Pathfinder 2e Bestiary 1     Pathfinder original/official source

Monster Codex     Pathfinder original/official source

Classic Monsters Revisited     Pathfinder original/official source

Monster Manual     D&D 5e original/official source

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

Ultimate Bestiary: Revenge Of The Horde     D&D 5e original/official source

Volo's Guide To Monsters     D&D 5e original/official source

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)

Monster Manual 3     D&D 4e (no source link)

Monster Manual 2     D&D 4e (no source link)

Dungeons And Dragons Essentials: Monster Vault     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

Monster Guide     World Of Warcraft RPG original/official source

Manual Of Monsters     World Of Warcraft RPG original/official source

Mystara Adversary Compendium I     Dragon Age original/official source

Low Fantasy Gaming Companion     Low Fantasy Gaming original/official source

Bestiary Of Cryptofauna     Old School Essentials (no source link)

Iron Falcon Handbook Of Monsters     OSR (no source link)

Baby Bestiary 1     Any original/official source