The Cataphract is the upgrade of the Heavy Cavalry in Age of Empires. It is the strongest hand cavalry in the game besides hero units. To upgrade the Heavy Cavalry to a Cataphract, 1,600 food and 750 gold is required after Metallurgy is researched. Only a certain number of civilizations have the ability to train this unit. Cataphract deals +5 damage bonus against all melee infantry units except for Academy units.
While a somewhat handy unit just by itself, the cost of the upgrade is so ridiculously high that many players find it pointless to research, as it generally does not pay off. In Death Matches, Cataphracts are considered to be a good way for non-chariot civilizations to take on Catapults.
"The cataphract was an improvement on ancient heavy cavalry represented by Alexander the Great’s Companions. The Companions wore only helmets, greaves, and cuirass (breastplate). Cataphracts wore chain mail that covered more of the body and often armored their horses partially also. This gave greater protection against arrows and hand-to-hand weapons. Cataphracts were very expensive to equip, however, and appeared in the armies of only the most warlike and wealthy cultures."