Extra Ballista was a technology in Age of Empires IV before the Naval rework. It could be researched at the Dock in the Castle Age. It adds a swivel ballista to Attack Ships. Swivel ballistae can fire in any direction and deal 15 damage. It was replaced by Swivel Cannon.
Swivel Cannon is the reworked version of Extra Ballista with only minor differences such as:
| Attribute |  Swivel Cannon
|
 Extra Ballista
|
|---|---|---|
| Age |  Imperial Age
|
 Castle Age
|
| Civilizations | All unless replaced by equivalent | All except Abbasid Dynasty and Delhi Sultanate |
| Gold | 350 | 250 |
| Time | 45 | 60 |
| Attack | 15 siege | 15 ranged |
