The Great Beasts are beast-like creatures that have outgrown other more diminutive monikers, generally growing to great size and power. While this can happen for any number of reasons, due to their general differences in regards to the original members of their species, Great Beasts are given special considerations to be a race of their own. This distinction is generally made based on their size, intelligence, influence, and notoriety.
While Great Beasts may come from myriad origins, some of the most recognizable and powerful Great Beasts emerged from direct contact with godhood. Agnahei the Eagle-God, the ancient enemy of the Callites, might attribute much of his power and intelligence to his interactions with the late god Calphost, who raised and educated the beast personally. Similarly, the Deep Serpent Serrolyth was spawned from the experiments of Coritem, and is thought to have once been an unremarkable snake.
It is notable that the term "Great Beast" is often used as hyperbole by many; for example, a shepherd who has had his flock ravaged by a lone wolf might refer to it as a Great Beast in order to emphasize its strength and brutality.