Cue the story of the priest or paladin of Helm or Torm who was so high level that even though they surrendered in order that the town not be sacked, they kept winning the single combats until the local legion ran out of them and had to send away for more. They still died eventually, but not before seriously depleting the chaplain corps of the entire host; the story is only known because this allowed the town to be retaken a few years later since the garrison was lacking divine magic support, and they weren't quite vicious enough in killing or silencing the witnesses.Life under goblinoid rule isn’t that bad, actually. The new law code will probably be a good deal harsher than the old one, but existing customs will be respected, and old political leaders will be left in charge as long as they act as a goblinoid puppets and helpfully point out dissenters. On religion, they are less flexible. Harmless harvest Gods and the like can be ignored as backwards superstitions, but any God of battle or war is a threat. The priests of such Gods are permitted a chance to turn to the worship of Maglubiyet, but if they refuse, they’re subjected to single combat against one hobgoblin priest after another until they fall. Temples of such conquered Gods are thoroughly converted into temples of Maglubiyet, with the alter being turned into a chopping block.