There's a nasty enemy out there, possibly an Eldritch Abomination, God Of Evil, or just a very powerful Evil Overlord. Even the gods are helpless before it, or so it seems. In fact, it turns out that while the gods are vulnerable to this enemy, a mortal is less so, so it's up to a mortal (i.e. Our Hero) to save the day.
A variation on this is that the gods are bound by certain rules that an [...] [tvtropes.org]