The Hydra Flak Tank, also known simply as the Hydra, is the main mobile anti-air artillery piece of the Astra Militarum. It is produced on hundreds of Forge Worlds across the Imperium and is widely-used in nearly every regiment. The Hydra, like many other Imperial military vehicles, is based on the Chimera armoured personnel carrier chassis, and is armed with a set of twin-linked Hydra Autocannons. Hydra Autocannons are a set of long barrelled Autocannons mounted on a turret with highly sophisticated tracking and targeting equipment. The Hydra is used to defend important ground units such as Imperial Guard artillery batteries and armoured columns from enemy air attacks. Non-mobile units or structures are usually defended by a Hydra Platform, a stationary version of the Hydra Autocannon, while the Hydra itself is generally deployed with mobile units. The Hydra's powerful guns are capable of quickly reducing enemy aircraft to smoking debris, but they can also be levelled towards the ground to engage enemy infantry and lightly armoured vehicles when circumstances warrant.

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