Skarga became a valued adviser to the King, and Sigismund became so fond of him that when the priest considered retirement, Sigismund rejected this, requesting that he remain at court for as long as possible. As part of his Counter-Reformation policies, Skarga was also a major proponent of the Union of Brest, a merger between the Roman Catholic Church and a faction of the Eastern Orthodox Church. His influence on King Sigismund, whom he supported (or encouraged) in opposing religious tolerance and seeking to strengthen royal power, was a factor that has been cited as a cause of the civil war—the (ultimately unsuccessful) Zebrzydowski Rebellion of 1606—in which the royal faction confronted a popular movement among the nobility, led by the Zebrzydowski family, who sought to depose Sigismund. Some critics referred to Skarga as "the principal mischief-maker of the Kingdom" (in the Latin, "pracecipuus turbator Regnii"). In 1611 he delivered his final sermon before the Sejm and published his final work, an ideological testament, Wzywanie do jednej zbawiennej wiary (A Call for One Redeeming Faith). He remained Sigismund's court preacher until April 1612, four months before his death. Skarga died on 27 September 1612 and was buried in the Saints Peter and Paul Church in Kraków. Writer In addition to being a popular and well-known preacher, Skarga was the author of numerous theological texts and polemics, and it is as a writer that his fame has endured. His two most important works are The Lives of the Saints (Żywoty świętych, 1579) and Sejm Sermons (Kazania Sejmowe, 1597). The former, a hagiography, won him fame in his lifetime, while the Sermons gained recognition only in subsequent centuries, during the Partitions of Poland. Tazbir describes the Lives as Skarga's chief work and as a major attack on the religious tolerance promoted by the Warsaw Confederation. The book was immensely popular, the first edition selling out by 1583. A second edition was published in 1585, and by the mid-17th century twelve editions had been printed, making it one of the most popular books published in Poland and Lithuania in that era (rivaled by the Kronika Polska—Polish Chronicles—of Marcin Bielski). It was Skarga's most popular work and continued to rank highly with Polish readers until the 18th and 19th centuries, when it was eclipsed by his Sermons. The Sermons, a political treatise composed in the guise of sermons, went almost unnoticed by contemporaries. In