If you wanted to add an element of absurdist humor, you could say his wrath has been invoked by temporarily raising a temple 1 inch off the ground to avoid structural damage while city engineers dig a sewer, and it's going to be placed back on the ground when complete He unleases a horde of slavering, underdark monstrosities on the city for what amounts to a six month public works project.
At some point, a wizened priest of Erathis sighs and says to the PCs: "This is why the other gods chained him up to begin with. He's kind of a dick..."