However, based on the descriptions, it's likely a bubonic plague, also known as the Black Death.
Here's why:
* Symptoms: The characters experience symptoms like swollen glands, fever, and blackening of the skin, which are consistent with bubonic plague.
* Time period: The story takes place in a medieval setting, which is the historical period of the Black Death.
* Social impact: The plague creates widespread panic, social breakdown, and a sense of impending doom, mirroring the real-world impact of the Black Death.
Although Crowley never specifically names the plague, the context and symptoms strongly suggest that it's a fictionalized version of the bubonic plague.