Conjunction of Worlds

Jon stepped into a bathroom and at the same time into a parallel world. Usually, this would not even be perceived, since the adjacent worlds are so similar the differences would be attributed to misrememberings. This time, the outworlder was unlucky. Jon stepped into a reality invaded by unknown forces, in which humans are assisted by a system made by a dead god. How will Jon survive inside this alien, but at the same time familiar, world?