Plot:

2 peoples/races engaged in a bitter war of religion (or not depending on story) against each other.

Each race seeks aid from its respective god. god's existence is not in doubt here, and each god gives his race information and aid assisting them against the other race (it is mostly information, dreams, visions, signs, augeries), and each race believes that because of these signs, there's is the true god, and the other's god is a fraud.

In reality, it is the same god on both sides, answering questions, giving information, dreams, visions, signs, augeries to each race simply because they were sought in the first place.

It might be that the god is not omnipotent, and therefore responsible for all things.

Or it could be that the god is omnipotent, and is answering queries from each race as simply as a man who is digging a hole might answer a question like "what are you doing man?" from another man round a corner who can't see him with a simple, "i am digging a hole."