I was expecting that the recollected fragments of the Mirror of Fate would lead to Gabriel's fight against his Inner Dracula, who would emerge through it, having retaken its true form, his vampire side against his human side in a realm inside the Mirror. However, probably through defeating his vampiric nature, it would have left him fatally wounded efectively, as his vampire body and human inner nature cannot survive without his vampiric inner nature. While in contorl of his full powers, he's only able to hold out long enough to fight against Satan. At this point, his soul ascends, to be finally reunited with Marie... leaving just his dark half left. It was defeated, but not killed, for as long as one side of him exists, his other side cannot be truly killed.
Or something along those lines, possibly with or without the last bit where only his dark side remaining while his soul passes on.