Once upon a time, there was a desperate druid. They sought the power to avenge their family. After consulting the faeries by speaking through the Nemeton, they found out that if they sacrificed a certain amount of people in a certain order, they would gain the powers needed to overcome virtually any adversary. However, this power would be on loan and required the Druid, who called themself Darach, to sacrifice their own life and the souls that they had used to gain power back to the tree after three years of completing their task.
However, after three years of time Darach failed to sacrifice himself back to the tree. Angered by his refusal to keep up their deal, the spirits of the Nemeton decided to send one of their greatest weapons out to retrieve the fallen Druid. This creature was a twisted, perverted amalgamation of damned souls who maintained their power by gathering the souls of the weak and the dying. This creature was eventually known as the Slaugh and quickly became the nightmare of Darach's original region as the Slaugh didn't directly go after him at the beginning. Many children and town elders lost their lives and became slaves to the Slaugh before the Slaugh took down Darach, dragging him and all of his collected souls back to the Nemeton he gained all this knowledge from. However, do to the fact that the Spirits of the Nemeton had no way of reigning this creature back in once it had been unleashed, the Slaugh continued to stay on Earth as a warning for all Druids who try to double back on a deal. For ever druid that takes the path of Darach, another Slaugh is released onto the Earth. As such, there were a lot of Slaugh distributed around the Anglo Saxon area during the time of the Roman occupation.