Pixie

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

Monstrosities     Swords & Wizardry original/official source

Angry Golem (web)     D&D 5e original/official source

OSE Encounter Activity Tables     Any original/official source

Pathfinder 1e Bestiary 1     Pathfinder original/official source

Mythic Monster Manual v1     Pathfinder original/official source

Faerie Bestiary     D&D 5e (no source link)

Beasts Of Legend: Fairy Tale Creatures     D&D 5e (no source link)

Neverland     D&D 5e (no source link)

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

AD&D Monster Manual     AD&D 1e (no source link)

QUERP Bestiary     QUERP original/official source

Jorgi's Bestiary     Trudvang Chronicles original/official source

Adventures Dark And Deep     Adventures Dark And Deep (no source link)