Vengeance Weapon Battery
The Wall of Martyrs Vengeance Weapon Battery is a heavily-armoured Imperial automated defence unit. Armed with either ballistic or directed energy cannons, they unleash a unholy amount of Dakka on any enemies that approach them by air or ground.
Countless billions of these batteries have been built over the course of the Imperium of Man's 10,000 year history and they remain a common sight on the battlefields of the 41st Millennium. Each Vengeance Weapon Battery sports a powerful cannon in a rotating turret, which is controlled by a simple automated firing system which will fire on any enemy unit it can sense. The thick plascrete walls of the battery make it invulnerable to all but siege weapons. Such is their durability that a Vengeance Weapon Battery will often remain operational long after any flesh and blood defenders have been killed or fled the battlefield.
The batteries are usually constructed forward of the main Imperial defence line, where their automated fire can serve as advance warning of an attack while driving the enemy into carefully pre-selected killing zones. They are also often used as automated weapon sentries to protect important locations, freeing up more mobile troops to be used elsewhere.
Vengeance Weapon Batteries are easy to construct and extremely robust, known to operate effectively for hundreds of standard years without requiring maintenance. They are usually armed with either a Battle Cannon, capable of taking on heavily armoured targets, a Punisher Gatling Cannon, capable of scything down entire units of infantry with a single volley, or a quad Icarus Pattern Lascannon, punching aircraft out of the skies with every salvo.
Most of what made these good, or at least playable, is gone in 8th. They're far too expensive and the battle cannon and punisher shots really need a better BS to work. They aren't the worst source of anti-aircraft firepower, especially if your faction has trouble getting it from other places, but the AA guns have very little chance of hitting anything that doesn't Fly.