From publisher blurb:
The tale of the Heresiarch begins in the Holy Land. The Knights of the Temple uncovered a cache of occult scrolls and magical paraphernalia in the lands near Bethlehem, including a strange sealed jar. They took their finds back to Europe, to the Chateau du Paynes, in order to study them and unlock their secrets. The chief of these researchers was a scholarly knight named Jerome, who broke the cipher on the jar’s inscription and discovered it contained a bound spirit called The Joyous One. In experimenting with the jar, the Templars accidentally freed the spirit...
This adventure takes the guardian priests into the city of Troyes, in search of a heretical preacher. The players must follow the trail of the first group of monks to tackle this problem, which leads them to the famous ‘hot fair’ of Troyes and a Templar castle beset by supernatural foes. The adventure is suitable for first or second-degree guardian priests.