Caestus Assault Ram

A Caestus Assault Ram belonging to the Astral Claws Space Marine chapter.

The Caestus Assault Ram is one of the Imperium's solution to one of the conundrums of space battle when needing to capture an enemy voidship/its crew/its contents: can't shoot it since there's a big risk of blowing it up for good, docking with it is too slow and hazardous and teleporting squads inside is hard and imprecise. So what do they do in such cases? Send manned vehicles to ram the target and deliver a bunch of warriors straight into the voidship's bowels without damaging it too much, of course! (Whether this is stupidly hilarious or hilariously stupid, we'll let you judge. Just know that the Boarding Torpedo has been part of 40k's fluff since basically forever.)

The Caestus is the Space Marine-only version, a vehicle originally developed for boarding other spacecraft. Its magna-melta fires a shot to weaken the enemy's hull, and then the armored prow smashes its way in. Meanwhile, the occupants are held in an inertial dampening restraint system that protects them from the shock of impact; each restraint harness is so big, it can accommodate a Terminator or a regular Space Marine, so the Caestus can deliver a full squad of any kind of Marine imaginable, limited only by the number of restraint harnesses aboard (thus ignoring the Bulky special rule). Once the Assault Ram has penetrated the enemy hull, the assault charges disrupt any defenders with a blast of shrapnel, the clamps release, the hatches drop, and the occupants charge into the fray.

Eventually, the Space Marines realized that the traits that made the Caestus so good at assaulting spacecraft made it very well-suited for ground attack as well. The magna-melta doesn't care whether it's melting a hull, a bunker, or a tank, and the restraint system and durable internal structure and hull meant that the Caestus could make steep orbital drops into zones too dangerous for a Thunderhawk or Drop Pod, especially once it had been upgraded with anti-gravity panels like the Land Speeder. Its frontal reinforcement, meant to ram its way into the often metres-thick outer hull of a capital voidship, also made it rather good at ramming pretty much everything else. So now some Space Marine chapters make ground assaults using Metal Boxes falling from the sky like Steel Rain. Speaking of which, this would work extra well if combined with Deathwind drop pod attacks. Those always come before manned drop pods come in, so the enemy would not be expecting this giant double-penis to shove deep into their threats and face-fuck them with its terribly deadly load.

The Caestus Assault Ram's model was created by Forge World for their Imperial Armour volumes covering the Badab War. Its rules are also now covered in Forge World's Horus Heresy series, confirming it was in use by many Legions during the 30k era, particularly the Imperial Fists Legion that often treats void warfare as a three-dimensional siege in space, with heavy preference for boarding actions by their Terminators and Breacher Squads delivered via Caestus.

Incidentally shares its name with a sort of Roman fighting glove weighted with iron or lead.

Also incidentally, this ship is a penis. Just look at it, before it hides itself fins deep into whatever orifice it blows its hot load into.

Also for when blowing up a giant space ship just isn't enough, one has to give it the Emprahs hot dickings to adeptus inseminate it, and fuck it to death.

While the quality of the game itself is a matter of opinion, the intro movie for the console game Kill Team showcases the Caestus Assault Ram quite nicely:

The Fan series "Astartes" has an epic clip of it's use as well:

Vehicles of the Imperium of Man
Walkers Dreadnought - Nemesis Dreadknight - Ironstrider Ballistarius
Onager Dunecrawler - Penitent Engine - Sentinel - Sydonian Dragoon
Transports Chimera - Crassus Armored Assault Transport - Drop Pod - Goliath Truck
Gorgon Armored Assault Transport - Hades Breaching Drill - Immolator
Pegasus AAV - Razorback Transport - Repressor - Rhino Transport - Taurox - Testudo
Trojan Support Vehicle - Triaros Armoured Conveyer - Tunneling Transport Vehicles
Atlas Recovery Tank - Achilles Ridgerunner - Bane Wolf - Bike Squad - Centaur Utility Vehicle
Cyclops Demolition Vehicle - Devil Dog - Hellhound - Land Crawler - Pegasus AFV
Salamander Reconnaissance Tank - Scylla Light Tank - Siegfried - Tauros - Venator - Wolfquad
Caladius Grav-Tank - Krios Battle Tank - Land Raider - Leman Russ Battle Tank - Predator
Ragnarok - Sabre Tank Hunter - Sicaran Battle Tank - Spartan Assault Tank - Vindicator
Ordnance Basilisk Artillery Gun - Colossus Bombard - Deathstrike Missile Launcher
Exorcist - Griffon Heavy Mortar Carrier - Hunter - Hydra Flak Tank
Manticore Launcher Tank - Medusa Siege Gun - Rapier Armoured Carrier
Stalker - Thunderfire Cannon - Whirlwind - Wyvern Suppression Tank
Baneblade - Capitol Imperialis - Cerberus Heavy Tank Destroyer
Fellblade - Leviathan - Macharius Heavy Tank - Macrocarid Explorator
Malcador Heavy Tank - Mastodon - Ordinatus - Typhon Heavy Siege Tank
Skimmers Javelin Attack Speeder - Grav-Rhino - Land Speeder - Pallas Grav-Attack
Flyers Archaeocopter - Caestus Assault Ram - Corvus Blackstar - Fire Raptor - Nephilim Jetfighter
Sky Talon - Space Marine Landing Craft - Storm Eagle - Stormbird - Stormhawk
Stormraven - Stormtalon - Stormwolf - Thunderhawk - Valkyrie - Vendetta - Vulture
Fighters &
Avenger Strike Fighter - Lightning Fighter - Marauder Bomber
Stormfang - Thunderbolt Fighter - Xiphon Interceptor
Spacecraft Aquila Lander - Arvus Lighter - Boarding Torpedo - Devourer Dropship
Faustus Interceptor - Fury Interceptor - Shark Assault Boat - Starhawk Bomber
Tetrarch Heavy Lander
Titans Imperial Knight - Warhound Scout Titan - Reaver Battle Titan
Warlord Battle Titan - Warbringer Nemesis Titan - Emperor Battle Titan
Forces of the Codex Compliant Astartes
Command: Apothecary - Brother-Captain - Brother-Sergeant - Chaplain - Chapter Master
Command Squad - Honour Guard - Librarian - Techmarine
Troops: Assault Squad - Centurion Squad - Chapter Serf - Devastator Squad
Scout Squad - Tactical Squad - Terminator Squad - Veteran Squad
Transports: Drop Pod - Land Raider - Mastodon Heavy Assault Transport
Razorback Transport - Rhino Transport - Spartan Assault Tank - Termite
Vehicles: Bike Squad - Dreadnought - Javelin Attack Speeder - Jetbike - Land Speeder
Predator Tank - Sabre Tank Hunter - Sicaran Battle Tank - Vindicator
Ordnance: Hunter - Legion Arquitor Bombard - Rapier Armoured Carrier - Stalker
Thunderfire Cannon - Whirlwind
Flyers: Caestus Assault Ram - Fire Raptor - Landing Craft - Storm Eagle - Stormbird
Stormhawk - Stormraven - Stormtalon - Thunderhawk - Xiphon Interceptor
Superheavy Tanks: Cerberus Heavy Tank Destroyer - Fellblade Super-Heavy Tank
Typhon Heavy Siege Tank
Spacecraft: Battle Barge - Strike Cruiser
Allied Space Marines: Fallen Angel - Primaris Marine - Blood Angels - Dark Angels
Deathwatch - Grey Knights - Space Wolves