Thy Fearful Symmetry

The end of the world started in Glasgow, with a kiss.
Two people - two creatures - fated to be eternal enemies downed their blazing spears and loved. To do so, they broke rules hardwired into the DNA of the universe.
The universe noticed. The universe broke.
Now Heaven and Hell are hunting them. Nobody on Earth can help them. Worst of all, the fabric of reality is unravelling around them, the Apocalypse has been brought forward a millennium, and it might all be their fault.
On cold streets, the last tattered remnants of humanity must draw faith in a world that has no more use for them. As the masses pray and crawl on bloody knees, the few must restore the fearful symmetry between good and evil - for the sake of all.
Blood will flow. Days will end. Fire will fall.