|This article is about the unit in Age of Empires II. For the unit in Age of Mythology, see Onager (Age of Mythology).|
|“||Stronger than Mangonel. Wheeled siege weapon used to attack a small mass of units.||”|
|—Age of Empires II description|
The Onager is a ranged siege unit in Age of Empires II that can be trained at the Siege Workshop once the Imperial Age is reached. It is primarily used against large groups of enemies. Its high attack and splash damage make it a powerful unit, especially against archers and slow-moving units. Its main offsets are its projectile speed, minimum range, and tendency to harm friendly units caught in its blast. Onagers can attack ground and .
Onagers are devastating against archers and slow-moving units, but cannot defend themselves against most melee units. Therefore, they need to be guarded in most situations. Archers are often used because the player's melee units can be damaged by their own Onagers if they are not careful. But archers do not cover the Onager's main weakness adequately, which is cavalry. Therefore, Onagers are also often paired with Halberdiers. That combination is used often with the Celts and Slavs, who both have bonuses affecting Onagers and Halberdiers.
While the Onager upgrade is fairly expensive at 800 food and a whopping 500 gold, it provides more attack, +1 range, +1 pierce armor, and slightly more HP. Since The Forgotten, Onagers are able to cut down trees, making them valuable in maps with large areas of forests like Black Forest by enabling the player to attack from behind a forest. It is visually distinguishable by a thicker more reinforced appearance. Overall it is a worthwhile upgrade when multiple Mangonels are being deployed.
|Unit strengths and weaknesses|
|Strong vs.||Buildings, Villagers, archers, Scorpions, Battering Rams, Trebuchets, units in dense formations|
|Weak vs.||Melee units especially Magyar Huszars and other melee cavalry, Mangudai, Woad Raiders, Condottieri, Eagle Warriors, Bombard Cannons|
|Hit points||Furor Celtica ( , Celts only)|
|Attack|| Siege Engineers (+20% attack against buildings)|
Torsion Engines (increases blast damage radius, Ethiopians only)
|Range|| Siege Engineers (+1)|
Shinkichon ( , Koreans only)
|Armor||Ironclad (+4/+0, Teutons only)|
|Movement Speed||Drill (+50%, Mongols only)|
|Conversion defense|| Faith|
- Aztecs: Onagers are created 11% faster.
- Bulgarians: Upgrading to Siege Onagers costs 50% less food.
- Burmese: Researching Faith is 50% cheaper.
- Celts: Onagers fire 25% faster. Onagers can convert herdables even if enemy units are next to them.
- Chinese: Technologies that benefit Onagers are 20% cheaper.
- Italians: Researching Chemistry is 33% cheaper.
- Portuguese: Onagers cost less gold. Upgrades that benefit Onagers are researched 30% faster.
- Slavs: Onagers are 15% cheaper.
- Tatars: Onagers deal +25% bonus damage from cliffs and elevations.
- A team containing Celts: Onagers are created and upgraded 20% faster.
- A team containing Koreans: Onagers .
- A team containing Malians: Researching Chemistry and Siege Engineers is 80% faster.
- A team containing Teutons: Onagers are more resistant to conversion.
- A team containing Lithuanians: Researching Heresy and Faith is 20% faster.
The Age of Kings
- Onagers move at a speed of 0.5.
- Researching Chemistry reduces the projectile speed from 3.5 to 2.9.
- Onagers now move at a speed of 0.6.
- Onagers gain +12 bonus damage against siege weapons.
- Heresy introduced.
- Celts: Furor Celtica introduced. It gives Onagers +50% HP.
- Mongols: Drill introduced.
- Koreans: Shinkichon initially gives Onagers +2 range. With patch 1.0b, the effect was reduced to +1.
- A team containing Koreans: Onagers have +1 range.
- Onagers can cut down trees.
- Researching Chemistry does not affect the projectile speed anymore.
- Celts: Furor Celtica now gives +40% HP to Onagers.
- Teutons: Ironclad introduced.
- A team containing Koreans: Onagers minimum range reduced by 2 (instead of +1 range).
- Bulgarians: With update 42848, Siege Workshop technologies cost -50% food.
- Portuguese: With update 42848, technologies are researched 30% faster.
|“||The onager was an improvement of the mangonel; it was larger, more powerful, and hurled a heavier payload for greater distance.||”|
|—Age of Empires II manual|
In reality, the onager was invented long before the mangonel, by the Ancient Romans. The Onager is credited as being the first Torsion Spring or Petraria Arcatinus-type catapult, as all catapults before that are called Ballistae and/or Scorpions.
The word onager derives from the Greek onagros, meaning "wild ass". It was named after the famously untameable onager or Asian wild ass (Equus hemionus), because it was said that the engine threw rocks as hard as the animal kicked.