Spined Devil

Background
The Spined Devil was summoned by Mason Silentdawn to terrorise the town of Preston, after its inhabitants slighted him by refusing to relocate.

It was described by townsfolk and in Lord Agren's memories as a shadowy winged demon, with glowing red eyes.

This Spined Devil was unlike any other. By stabbing a person with one of it's spines, it could transform them into a Ghoul that did it's bidding. It commanded a group of them to cover a statue in corpses. It's presence was also the origin of the magical fog that clung to the town, which blocked sound as well as visibility.

It seemed to be drawn to the sound of screaming women, proven when Aurora was used as bait by the Heroes. Having hidden nearby, the Heroes were able to ambush it and take it by surprise. It was slain by Belrun with an arrow to the heart, but not before nearly knocking out Rasend Dracon.

When it was killed, the infected people of Preston returned to their normal selves, and the fog disappeared.

Trivia

 * The Spined Devil is also referred to as a Horned Devil in the episode, which is a much more fearsome type of fiend.
 * In a post on Discord, Adam explained that due to their demonic heritage, Tieflings are immune to the infection. They would not be turned into Ghouls in the way that the people of Preston were.