Jaroslav was born as the illegitimate son of a Slavic man and a gypsy woman and left for dead near what is modern Germany. He was saved by a Franciscan friar who brought him to his monastery. The monks raised Jaroslav as a "collective son", all the while instilling him with shame and guilt about his heritage as a half-gypsy, which they corroborated with beatings. When Jaroslav had become a grown man, he had been turned into a figure full of fury that he channeled into his views of Man and God. He began to notice dissonances in how the monks lived and how they should have lived according to scripture.
Soon, he became convinced that it was his duty as a honest Christian to purge and reform the Church. Before the official Reformation took place, Jaroslav wandered across northern Germany, preaching his doctrine of holiness and purity to the peasants. When he realized that preaching alone would not change their ways, he assembled a militia and swept through their villages, burning clergy they deemed impure and destroying relics they deemed false.
His fervor and charisma earned him the attraction of a Brujah and his coterie, who offered Jaroslav the possibility to join them in their task to change the world. Captivated by his visitors' personal magnetism and persuasiveness, Jaroslav agreed. He threw himself fully into the world of the undead, believing to have sacrificed his own salvation to give it to others. His coterie members pointed at vampires and declared them servants of Satan, and Jaroslav would commit himself with every means to destroy them, making the first decades of his new existence a haze of blood and gore.
When the Camarilla was officially formed, Jaroslav entered torpor, hoping that the new formed sect would be able to end the vampiric meddling in mortal affairs. When he rose in the mid-17th century and stumbled across a Sabbat pack, his anger was again ignited. He gathered a coterie of like-minded Kindred and his carnage on Sabbat vampires inspired dread in even the Consistorium.
His fervor earned him the post of Archon under Justicar Carlak and later the post of Justicar himself. Jaroslav himself, however, is disgusted with both the traitors in the Sabbat and most of his fellow Camarilla vampires, seeing them nearly as corrupt as the Church in his youth. Special hatred is reserved for his fellow Justicar Anastasz di Zagreb and his Archon Theo Bell.