It's up to them

Although a deity, insulted by the offense of vow neglect, could indeed castigate the offender with a variety of misfortunes, the punishment is never seen to derive from a prearranged, conditional malediction. This illustrates a fundamental distinction between the vow and the oath. The curse in an oath establishes the nature of the punishment in advance while the vow leaves the penalty to the whim of the deities.— Cursed Are You!, page 36

<idle musing>
And given the unstable nature of some of those gods, I don't think that was supposed to be a comforting thought...
</idle musing>