The air stank of death. It was the smell of corpses and blood and grief. The sounds of coughing and crying filled the dirty streets. People hurried through the sea of bodies on the road, heads down. Terrified. Terrified of an evil they couldn't see, couldn't understand, couldn't stop. The disease seemed to have spread to the ground itself, which was stained with blood and the tears of the grieving. It was as though Hell had come up to the human world. Indeed, in this terrible time, demons really did walk the Earth.
Crowley struggled to maintain his usual swagger as he and the other demons moved through the streets of fourteenth century London. Hastur and Ligur walked with him, as well as a hoard of other demons, screaming victory and laughing as they saw the bodies stacked up against every house. Crowley felt sick. He didn't really do death. Minor inconveniences to extreme annoyances were more his style. This amount of pain and suffering made him acutely uncomfortable. the It all felt too much like Hell, the place Crowley had been hiding from for all of his life in Earth.
He pitied the humans, who were trying to help each other in vain. They were so, human. They wouldn't back down and submit to the death which filled their short lives. He wished he could help, and this somehow made everything worse. He was a demon, for Satan's sake! He couldn't go around wanting to save those whose lives he was supposed to be ruining. He was a terrible demon, but he was terrible at not being a demon too. The conflicting emotions muddled his thoughts, making his task all the harder. He had become too human to enjoy this, but not human enough to make it stop, to rebel. The best he could do was build a wall around his conscience with excessive alcohol during the parties in which the demons joyfully congratulated themselves on the pain that they caused every day.
It didn't help that he hadn't seen the angel for maybe half a century now. Normally Aziraphale's presence could make any painful task at least a little easier, and he could always rely on the angel to thwart him, so that a little less pain was caused. But no angelic amount of angelic healing was stopping this terrible plague which had crossed the land. Aziraphale was out there somewhere, desperately trying to save humans, while he, Crowley, was killing them off in their thousands. Telling lies about cures to make ailments worse, planting doubt and chaos in every mind. This carnage, it was all his fault.
Crowley knew that this would end one day, and that was the only thing getting him through it. He hoped never to experience anything like this again. When the hell on earth was finally over he would block it out of his mind and savour each year that took him further away from the fourteenth century.