Source: Bestiary 3, pg(s). 36
When the gods run out of patience for mortal insolence, they lash out through plagues, floods, and terrible servants, among which behemoths are the most well-known. Behemoths are shaped from the primal energies of creation, infused with elemental might, bound within a flesh-and-blood body and filled with righteousness and the thirst to destroy all in its path. These beasts are then unleashed upon the victims who are the most deserving of the wrath of the gods. Some gods turn aside the behemoths when their anger is appeased, while others pay no attention to removing them when their work is done. Entire worlds have been destroyed by behemoths, leaving aside naught but themselves as living monuments, waiting only for the right moment or a tragic accident to waken and ravage once again.
Marginally more intelligent than animals, behemoths can understand Aklo but cannot speak. Nothing less than a god or the most powerful artefacts can command a behemoth, but there is always a risk of betrayal.
Behemoths are most often unleashed by lawful or civilised gods. Gods of the natural world either are not inclined to punish mortals at all, or prefer to use natural disasters instead. Behemoths are incapable of reproduction.
Regardless of their nature, each behemoth suffers a single flaw by which it might be slain: a weakness against miracles and wishes. It has been theorised that this is the result of the imperfect binding of chaos to order, or divine caution against a behemoth's potential betrayal.