Heresy is a technology in Age of Empires II: The Conquerors that can be researched at the Monastery. Once researched, it causes own units that have been converted by an enemy Monk or Missionary to die instead of joining the opposing player. Converted buildings are destroyed.
Heresy is very useful, as it prevents the player's converted units from being able to attack and distract remaining troops. The technology helps minimize losses. Players should research Heresy if they anticipate an enemy attempt to Monk rush.
Given its high cost, especially for the Castle Age, however, it is not recommended to research Heresy if opposing players do not regularly use Monks for conversion purposes.
Note that with Heresy researched, a Konnik will die when converted, but still turn into a Dismounted Konnik that belongs to the original owner (instead of the converting player).
As seen in the table above, Heresy is notably absent from the technology trees of most civilizations with access to powerful units such as elephants, with the sole exception of the Malay (since their Battle Elephants are the weakest).
- Lithuanians: Researching Heresy is 20% faster.
- Generally speaking, the access or lack thereof to Heresy can be justified on historical grounds:
- The presence of Heresy may indicate the central character of religion in the military history of a civilisation: for example, the Berbers are responsible for the Islamisation of Spain in the 8th century, the Vikings and Lithuanians usually represent pagan armies fighting Christian forces, the Teutons formed an order of monk-warriors (the Teutonic Order) and the Spanish converted vast swathes of the American continent to Catholicism. All of these civilisations have access to Heresy.
- Among the civilizations introduced in Age of Empires II HD: Rise of the Rajas, only the Malay have access to Heresy. This may be a reference to books and studies written by scholars such as Marmaduke Dodsworth, who have stated that the Malay people are historically very resistant to conversion.
- The fact that civilizations with Elephants (with Malay excluded for gameplay balance purposes) do not have Heresy is a reference to how many battle elephants may often panic in fear in battle and would often trample on their own soldiers due to said fear. Furthermore, many armies would often capture an elephant from the enemy side during war and use them as part of their victory parade.
- Italians not having access to Heresy may be a reference to the absence of political unity in Italy throughout the Medieval period; it could also represent the Renaissance, which notoriously started in Italy and led to the birth of new secular philosophies that questioned the absolute authority of the Roman Catholic Church. It could also refer to the condottieri, whose loyalty was famously fickle.
- The fact that the Britons and the Burgundians lack Heresy might allude to the Protestant Reformation, which saw both Britain and the Low Countries renounce their loyalty to the Roman Catholic Church.
- Alternatively, the Burgundians not having Heresy could refer to the fact that during the Hundred Years War, they betrayed the French and sided with the English army. This can be seen in the last scenario of the The Grand Dukes of the West campaign, The Maid Falls, where Joan tells Philip the Good that he is a traitor to France.
- Bulgarians having Heresy but lacking Faith might reflect the fact that one of the most influential Gnostic movements in Medieval Europe, the Catharism, had its ideological roots in Bulgaria. The Cathar movement was banned by the Christian Church (both Catholic and Eastern Orthodox) and its followers were persecuted as heretics throughout Europe. Suspected Cathars were put through painful and usually lethal ordeals (auto-da-fe, act of faith) in which they had to prove their "faith" or die.
- Magyars having Heresy but lacking Faith might be a reference to their ancestors following Tengrism or shamanism before they adopted Christianity once they settled in the Carpathian Basin.
- Sicilians lack Heresy due to their religious tolerance, which is highlighted in the The Hautevilles campaign.
- The absence of Heresy for the Slavs is likely acknowledging the variety of faiths practiced by the Slavic peoples, with western groups like the Croats, Poles and Czechs following Roman Catholicism, groups in the east such as the Russians and Serbs practicing Eastern Orthodoxy, and other groups like the Bosnians following Sunni Islam.
- The Franks having Heresy is likely to be a reference to the extremely violent Cathar Crusade, where the Franks would represent both the Cathars of Southern France and the Catholic Crusaders from the rest of the country.
- The Persians and Indians lacking access to Heresy is presumably a reference to the expansion of Islam to Persia and Northern India during the Middle Ages: Persian Zoroastrianism and Indian Buddhism were nearly eradicated.
- Most of the East Asian civilizations (Chinese, Koreans, Japanese, and Vietnamese) lack access to Heresy, possibly due to their religious diversity during medieval times: for example, several religions such as Buddhism, Taoism and Confucianism coexisted in China, whereas in Japan, Buddhism established a solid presence without displacing the native Shinto religion.
- The absence of Heresy may also indicate the presence of secular (rather than religious) internecine conflict in the history of a civilization: such would be the case for the Britons (who went through The Anarchy and the Wars of the Roses) and the Japanese (who experienced civil strife during the Kamakura and Sengoku periods).
- Anarchy is also a unique technology for the Goths, so it is the possible reason why the Goths lack Heresy.
- It may be pointed out that the Byzantines have access to Heresy in spite of the several civil wars and general disunity they experienced in the Middle Ages, but the historical significance of such factors is still outweighed by the religiously-motivated invasions conducted by the Saracens, the Turks and the Catholic armies of the Fourth Crusade.
- The Tatars are a Khan civilization just like the Mongols, and yet they lack not only Heresy, but Faith as well, and are therefore the most vulnerable civilization against conversion. This might be a reference to the nearly immediate decline and fragmentation of the Timurid Empire following the death of Tamerlane.
- Heresy’s icon says [De] plurimis claris selectisque mulieribus opus prope divinum [novissime] congestum, which is a quote from Giovanni Boccaccio that roughly translates to ‘Concerning many famous and select women, a nearly divine work very recently gathered.’
- Neither of the two civilizations introduced in Lords of the West have access to Heresy.
|“||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|