I have a theory about the state of that Sarnori Smith-god.
Just a theory though.
We know he's dead. Really dead, from loosing all of his temples and most of his followers to the Dothraki.
He's not Yss who has dominion of life and death and can restore himself or linger in near-death for millenia.
He's not Tiamat who is a major Power in her own right even without the whole divine nonsense.
Just a human god who is as dead as a god can be without being totally forgotten.
But!
Right now he gets the prayer- and faith-income from millions of undead Sarnori. Or at least tens of thousands if only the intelligent ones count.
He can't fully use it, because he's too dead to just grow from it and has the wrong domains to restore himself. No storage-capacity.
But it's still like a sugar-rush, usable energy without longterm-benefit.
That's how he can basically use a miracle or divine smiting in every combat-round, he directly converts the faith that he can't use otherwise into divine action.
If this theory were true it would be good for us on the one hand, because it means he's personally not nearly as strong as a god with his faith-income should be.
And it would be bad, because it means until we have either laid to rest most of Sarnor, or until we have destroyed his direct connections to this plane (likely including the statue-body from the Omake) or maybe his divine corpse wherever that may be, he will continue being a nuisance with a high frequency of divine interventions.