The Warlock Trials (837-843) came at a time where the Church had unprecedented power and authority. The Church always stood against arcane magic. Believing that power from other sources than the divine could not be trusted.
Using their new found influence, the Church started rounding up magicians to hold them accountable for the Black Plague Death that was released on humanity a few years earlier. This crusade was carried out under the guise of finding those responsible.
The sect of the church responsible was the Avesti sect. These heresy seekers sought to elevate their position in the Church by riding the fear of the populace.
The Church would send out it's teams to hunt down arcane spell casters. Once found they would be captured, sometimes killed, and brought back to Tera for trial. The trial depended on the inquisitor who was put in charge of the case. Some mages were simply put under the scrutiny of spells like the Zone of Truth. While other inquisitors claimed these spells could be circumnavigated. The harsher trials lead to death or permanent injury. Common punishments were tongue or hand removal.
Finally the Circle of Amalthea and the Eskatonic Order were able to garner enough support to form a Cardinal Synod (842) to lessen the extreme punishments and formalize the proceedings. After another year they were able to end the official trials.