The sorcerers it was an organisation of dark magic practitioners who didn't have an official name. An anonymous association who were the core villain of the novel Priestess and Dragons written by Hazel Walters.
Although the main book revolved around the Von Drakkar family politics the existence of the group shaped the events for everything.
In the original plot, Callista was the one who uncovered the mystery with the help of Lucian and Cedric, making her the heroine of this world.
Callista found out the Dark sorcerers were an ancient group who had been operating in the shadows, their goal was simple: to take down the royal family and rewrite Draconia's history.
Lives were lost in these plots, slaughtered, assassinated, poisoned and plagued. They were behind several events.
The winter hunt
The crop poisoning
The plague which ravaged during the last winter
The perfectly coordinated attack during the spring festival
And other minor events.