'In-game icon of the Oprichnik.'
The Oprichnik are Heavy Cavalry units unique to the Russians in Age of Empires III. They are available at the Stable once Fortress Age is reached. Although the Oprichnik is effective against both Light Infantry and Artillery Units, they lack the melee attack and large hit points possessed by other heavy cavalry, making them rather ineffective in melee combat. However, Oprichniks sacrifices this for their ability to deal bonus damage against Villagers and an additional bonus against Artillery. In addition, they also have a high siege attack against Buildings that other heavy cavalry do not have. This provides Oprichniks strong offensive capabilities in early games lacked by other heavy cavalry.
Since Oprichniks have high siege damage and a bonus against settlers, they are very useful for keeping up pressure by raiding enemy villagers and buildings early in the game. Even if unleashed in small groups, the overall result could be devastating to the victim if unleashed at the perfect strategic location. Their very high siege attack enables them to wipe out entire towns even in a moderately sized army if there is little to no resistance from the enemy. Note they are sort of like the bullies on the playground: They kill things smaller than them and should flee from military units. When raiding an enemy town use them to take out the outposts and forts (if any) while other units attack non-aggressive buildings. This way the outposts/forts will be destroyed before they can do major damage. Make sure not to engage Oprichniks in battle with other military units unless necessary, or if there is no worry about losing (victory is definite).
A strategic way of using Oprichniks in a battle is by taking advantage of their speed to flank an opposing army from one or both sides. Because of their bonus against artillery, they can be used them to take out enemy cannon or light infantry that may pose a threat to friendly infantry. When raiding an enemy town, use them to take out defensive buildings like outposts or offensive buildings like barracks, stables, and artillery foundaries. Also, let a small group run loose within the town to kill settlers. To maximize the effectiveness of the Oprichnik, upgrade it at least to Guard or to Imperial if possible. Use cards like "Cavalry Combat" and "Boyars" that increase the hitpoints and attack of the unit as well as the "Cavalry Cuirass" upgrade from the Arsenal. When fully upgraded with the upgrades listed above, the Oprichnik will have a good 575 hitpoints, a decent 40 hand attack, and a whopping 150 siege attack.
Oprichniks benefit from Technologies found in the Arsenal though, better improvements for them are available at the Stable once the player advances through the Ages.
The Guard Oprichnik is the next rank and is the first major upgrade of the Oprichnik. The Technology needed to produce them is available in the Industrial Age at the Stable. 1000 Wood and 1000 Coin is required prior to research. This Technology improves the hit points and the attack of the Oprichnik greatly however the multipliers as well as their speed remains the same.
The Imperial Oprichnik is the next and final upgrade of the Oprichnik. The technology needed to produce them is available during the Imperial Age at the Barracks. 1600 Wood and 1600 Coin is required prior to research. This technology improves the hit points and the attack of the Oprichnik much greatly than the Guard Upgrade however the multipliers as well as their speed remains the same.
The Oprichniks were a group of secret police officers during the period in which Ivan the Terrible ruled. They are primarily used to suppress rebellions and are used to hunt down villagers and peasants whenever they opposed the regime.