Heresy

Heresy is a Technology available in Age of Empires II: The Conquerors as one of the new additions to the game accompanying that expansion pack.

This technology is incredibly useful, as it prevents enemy Monks from converting any of the player's units. When an enemy monk is converting one of the player's units, instead of it being transferred to the opposing team, the unit merely dies when converted. This means that players who have researched heresy do not need to fear their own units being used against them in battle,also make managing army more easier than usually and heresy can inly be researched by some civilization.

Real Info
Heresy refers to contrary views of religious doctrine, or dogma. It was considered a crime punishable by death in the Middle Ages, represented in-game by monks killing enemy units rather than converting them.