Heresy is very useful, as it prevents the player's own units from being converted to the enemy and turned against each other. Since a converted unit now dies, it does not distract and harm the remaining troops anymore. It is highly recommended to research Heresy if the enemy attempts a Monk rush. Heresy ensures that the troops are organized in battle and to minimize losses. Given its high cost, however, it is not recommended to research Heresy if opposing players do not regularly use Monks for conversion purposes.
Heresy is notoriously absent from the technology trees of most civilizations with access to elephant units of some kind, which are powerful, but prone to fall victim to conversion. The only exception are the Malay, who have the cheapest and weakest Battle Elephants.
Civilization bonuses Edit
“As the Middle Ages progressed, Christianity in Europe faced a number of challenges, including heresy. This word came into use in the 13th century to define an opinion or doctrine that was contrary to church dogma. New opinions popped up at an alarming rate. Philosophers studying the Bible suggested new interpretations. Contact with pagan beliefs led to distortions of dogma in the hinterlands. Anyone who attempted to newly interpret the lessons of the Bible risked being accused of heresy. Coming to believe in a heretical position was seen by church leaders as a supreme sin, and many people condemned as heretics were burned at the stake.”—The Conquerors manual