Heresy is the practice of a belief opposed to the established religion. In the Dark Ages and the Middle Ages, various heresies sprung up against the major religions, with Iconoclasm, the Wycliffites, Hussites, Cathars, and the Protestants going against Christianity, Mazdakism and Manichaeism challenged Zoroastrianism, the Samaritans challenged Judaism, and the Druze and Yazidis challenged Islam; the various heresies were threats to established religious authority. Most heretics would be burnt at the stake, and heretics rose in rebellion against their lords at times. By the start of the Renissance, not many heresies were left.