In theology the name Seraphim refers to a type of angel. Therefore, one could conclude the 2 main characters are angels that have fallen from grace. They battle eachother from the mountain tops (Heaven) to the hot desert (Hell).
After going over the falls, Gideon mysteriously surfaces with his saddlebags, even though it had been draped over his fur-coated arm and he had to struggle out of the coat when it got snagged on some branches underwater at the bottom of the falls.