“Rain patters off the carapace of Tormentor and a slow, steady thrum is emitted from the ion reactor as it idles on silent running. With the Knight in this condition, I feel the closeness of the ruined structure I have adopted to be my ambush position. These feelings spike occasionally into pangs of claustrophobia; though I know this to be Tormentors spirit longing for the engagement to begin.

With no active augury and unable to move the Knight I’m reliant on the rest of the House Ærthegn Hunter Killer group to alert me to threats outside of my immediate forward arc. They too are similarly dug into ambush hides.

The rain squalls into a tumultuous storm. Good. This will send the enemy augurs into spasm. The storm rains down in a violent drumbeat. Lightning flashes across the sky, illuminating the bleak and war torn city outskirts ahead of me.

Another flash of lightning draws a reflection from the ground. It’s 7 kilometres out. Tormentors ocular augmetics draw a small shudder of power from the ion reactor as I command them to zoom and enhance the image.

A House Vyronii Cerastus Atropos with Command markings moves delicately through the ruins in a half crouch, its movements only given away by the intermittent reflections of lightning off the carapace. A careful one, this Commander is; but his care has been defeated by the weather.

The 4 Ærtheyn Moriaxi stationed in forward observation positions at the 5 kilometre mark datasquirt targetry to me. Their directional antennas and very low frequency emissions untraceable by the advancing foe.

The ion reactor rumbles as I close my eyes and sink into the manifold. I pull slightly on the reactor to lock passive targeting augurs on the Atrapos; Tormentor replies in kind by adjusting onto target shuddering millimetre by millimetre. Small sections of rubble fall to the floor – not enough to be noticed at distance.

The Moriaxi issue one final targetry package to the group. 6 kilometres out;

1 Atrapos.

8 Questoris Errants.

2 Armiger.

Targets are assigned.

At 5.5 kilometres, Tormentors reactor screams into full, glorious life. The reactor lets out a higher pitched scream as I demand yet more power; an overcharge to the weapons. A thunderclap rings out as 4 streams of bright red fury reach out and touch the Atrapos. It’s shields explode immediately. The Magna Lascannons punch clean through the Atrapos cockpit, blowing out its reactor in a green plume of fire and shrapnel. The dead Atrapos stands still, rain hammering off its agonised carapace.

Around it, 5 Errants are already destroyed. Thermal alarms ring out in my manifold, before falling silent as the system vents heat from the Magna Lascannons. I target an Errant running for the nearest cover as it is engulfed in enfilading fire. It makes it, but I fire through the ruins. I am rewarded by a green tinged explosion spurting out low to the ground.

The others fall quickly, with minimal damage to the Hunter Killer group. A Dark Mechanicum combat salvage team quickly fans out of cover behind me to loot the dead.

Tormentor stands at my command, stepping free of the collapsing ruin. We move amongst the Dark Mechanicum, ready to put down those with delusions of being heroes. I approach the Errant I downed. It is missing a leg and a weapon arm. It’s pilot attempts to roll and face me as I approach. As it brings the weapon up, my Lascannons cut the weapon free. I lower the right Magna Lascannon so the muzzle is almost touching the cockpit hatch. The shot is precision, blowing through the hatch and out behind its chest armour plate.

When the salvage is complete, we push to new positions and dig in. They will send more.

Let them come.

Let them burn in their thrones as the Night Lords decimate those who send them.

Seneschal Hans Jurgen, House Ærthegn

The Acastus class is the largest of the Knight chassis and is comprised of two variants; the more common Porphyrion and the much rarer Asterius. Both are true giants compared to their Knight brethren, even towering over Cerastus class Knights and closer in height to a Warhound Titan. Their chassis is protected by heavily armoured panels and a powerful ion shield making them impervious to all but the heaviest firepower. Their enhanced reactors provide vast amounts of power to their weapons systems, able to engage the enemy with devastating firepower. Porphyrion pilots are known by other chassis class pilots as “kin-killers” due to the manner in which they are used; the destruction of other Knights.

Introduced in Campaign book VII – Inferno (page 296) this behemoth of war is able to be taken as part of a Panoply of War – Legiones Astartes rejoice!


The Acastus Porphyrion has its latest set of rules in FAQ 1.1 found Here. Originally it cost a mere 460 points. This was fairly low considering what it is capable of. It now sits at 560 points base, which is no small sum, but far more appropriate for it.

The Acastus Porphyrion has a basic stat line of:


As with most of the Super-heavy walkers, this stat-line is at first glance fairly underwhelming considering the price of it. This initial assessment is made worse by the fact that, at face value, the Leviathan Siege Dreadnought is slightly less well armoured (at AV 13/13/12) and has an all-facings 4+ Invulnerable save with 4 HP for c.320pts. This is mostly down to the fact that the Leviathan is very well written and pointed, and also down to the fact that at face value, you miss most of the things that make the Porphyrion seriously dangerous.

As a Vehicle (Super Heavy Walker), the Porphyrion uses the Super-Heavy Vehicle rules for Shooting, Vehicle Damage and Catastrophic damage. Moving a full 12″ in the movement phase, their threat range is genuinely terrifying, allowing for deployment in cover and manoeuvring to fire in T1 with minimal concern.

Additionally, they have the chance to perform Stomp attacks. This consists of D3 stomps and is made in addition to the Super-Heavy walkers normal attacks. Stomp occurs at Initiative 1 and does not enable you to pile in further at that step. Stomping does allow you to “stomp forward” but the model doesn’t physically move. Imagine it more as giant metal happy feet movements.

Close combat is made more effective by the fact that Vehicle (Super-heavy walker) causes Fear. If at the start of each Fight sub-phase, a unit is in base contact with the Porphyrion, it must take a Fear Test. If it fails, it fights with a Weapon Skill of 1 for the rest of the Fight sub-phase.

Even though the Porphyrion does not mount dedicated melee weapons, it does have a further ability to cause damage. With Hammer of Wrath, when it charges in it makes one additional attack at Strength 10, AP -. As with Stomp, this occurs at a dedicated Initiative step, in this case Initiative 10, but does not confer a pile in move. If the target is a vehicle, the hit is resolved against the facing armour value.

With movement already benefiting from Vehicle (Super-heavy walker), the addition of a further sub rule for Move Through Cover improves it even more. Move through cover means that you roll an additional D6 when moving through difficult terrain and is not slowed by charging through it. This means when you’re moving through difficult terrain, you’re rolling 3D6 and picking the highest dice roll. Remembering that the Vehicle (Super-heavy walker) rule then asks you to double the roll value. Any model with Move Through Cover automatically passes Dangerous Terrain Tests. This means that your movement is pretty much ignoring any terrain issues that you run into.

Invincible Behemoth effectively means that when a Destroyed, Wrecked or Explodes! result is rolled against the Porphyrion, it inflicts D3 hull points instead. One sub rule of this is that any attacks or abilities that permanently lower the AV of the chassis do not affect it. This does not stop rules such as Lance working.

Relentless grants the ability to move and shoot Heavy, Salvo or Ordnance weapons as if they had remained stationary. In this case, Ordnance. They are also able to charge in the same turn those weapons have fired. This means that you have no issues with movement to enable shots from the secondary weapons this platform has available to it.

Smash means that all of the close combat attacks are resolved at AP 2, with the exception of Hammer of Wrath unless it has an AP 1 weapon, which this does not.

Finally, you have Strikedown (All). Any non-vehicle model that suffers at least one unsaved wound or passes one or more saving throws against an attack with this rule moves as if it were in difficult terrain until the end of its next turn.

This brings us to the end of the sub rules that are provided by Vehicle (Super-heavy walker). However we aren’t quite at the end of the basic rules for the Acastus-class.

All Knights are equipped with an Ion Shield. When it is deployed, and at the start of each opposing sides shooting phase, the controlling player declares the position of the the Ion Shield. This can either be front, rear, right side or left side. This grants the Knight a 4+ invulnerable save on that facing for shooting attacks only.

For Mechanicum, the rule Blessed Autosimulacra is the final basic rule. It if has suffered hull point damage, at the end of the controlling players turn roll a D6, on a 6, one lost hull point is restored. This ties in well with Magos and Arch Magos Dominus Battlesmith rule and even more so if they have a Machinator array.

Overall, the ruleset makes the Porphyrion quite the opposing force to deal with. The mere presence of one will force one of two deployment reactions; stand and fight or hide. The former will see you having to choose the greater threat to the Knight and direct the Ion Shield as such. Take the time to consider the likely plan of action as there’s no Armoured Ceramite on a Knight. Therefore they’re very weak to Melta. The final thing to consider on the shield facing is that the humble Lascannon will glance on 5 from the front, 4 from the side and 3 from the rear. With the prevalence of that weapon, especially on Fast Skimmer platforms such as Javelin Speeders the mentality of thinking a turn ahead will help keep it alive.

An imposing model, the Acastus Porphyrion will undoubtedly attract enemy fire from the outset.


The core function of the Porphyrion is to bring firepower to bear, be it on their kin, fortification or individual targets. So, lets look at those weapons.

Outfitted with two twin-linked Magna Lascannon that dominate its frame the Porphyrion is a monster. The Magna Lascannon is a template weapon, using a Large Blast 5″ template – so again, you’re benefiting from the re-roll armour penetration.

Magna Lascannon72″102Ordnance 2, Large Blast 5″

Getting straight into the reason the Porphyrion is such a monster; Ordnance 2 per Magna Lascannon. That means you’re dropping 4 twin-linked Large Blast 5″ templates a turn at BS5 with the primary weapons alone. It’s a strong weapon. The solid counter to this is a flare shield – which reduces the weapons strength by 2 due to the rule of it affecting blast weapons as such. The counter to that counter is the movement ability of the Porphyrion to engage the side or rear armour. It really does take the game deep into the region of manoeuvre warfare.

So the Primary armament is able to gut enemy targets, but what about the Secondaries?


The Porphyrion is the aggressive players wet dream mainly because its secondaries support it so well.

Ironstorm Missile Pod72″64Ordnance 1, Massive Blast 7″
Helios Defence Missiles60″82Heavy 2, Skyfire, Interceptor
Autocannon48″74Heavy 2
Lascannon48″92Heavy 1
Irad-CleanserTemplate25Assault 1, Fleshbane, Rad-Phage

Ironstorm missiles and Helios Defence missiles are a free swap. I generally look to configure Porphyrion with Helios Defence Missiles. This is mainly due to the fact the Night Lords and Dark Mechanicum armies I run have little in the way of dedicated anti-air and I face quite a few aircraft in our group. Ironstorm missiles do well at harassing infantry and will certainly cause issues for your enemy, but they’re balanced by being only AP4. This is more that enough to smash most Mechanicum and Militia troops however.

The Autocannons are free as they’re equipped as standard, but each Lascannon will set you back 10pts each. Finally, the Irad Cleanser is a free swap, adding some further anti-infantry with Fleshbane and Rad-phage helping to clear squads from the Porphyrions path. Personally, I look to run with Lascannons, amping up the threat to anti-armour as much as possible. That said, there’s an argument to using the Irad Cleanser as a point defence weapon to defend the Porphyrion against enemy infantry.


Occular Augmetics (10pts): This upgrade grants the Night Vision special rule and allows the Knight to re-roll results of 1 on the vehicle damage table when they’re shooting at 12″ or less. However, the Night Vison rule on the Porphyrion seriously helps when fighting against Night Lords or in a mission where Night Fighting is in effect by negating the cover save brought in by Night Fighting. It’s a personal decision and based entirely on your opponent, table and chassis in use in my opinion.


The Acastus Porphyrion is a staple of the Horus Heresy and for good reason. It’s a big, complex and beautiful model to build, paint and display. Though care should be taken around the leg panels as they have specific attachment points on the struts and overlapping armour plates can foul meaning some poses are difficult to engineer.

From a gaming standpoint it really depends on your local “meta”. Fast moving armies will cause issues for the Porphyrion by presenting multiple threat facings. Whereas with Titans, you can pretty much wade into the fight with little consideration to the threats, such is their defensive and offensive capability, with the Porphyrion it’s all about positioning and movement to gain better target pictures whilst assessing the placement of the ion shield to best protect it.

Offensively, there’s almost nothing else aside from the Mechanicum Ordinatus Ulator or Titans that provide a genuine full-table threat like the Acastus-class. The former through its unique weapon profile, the latter through overwhelming weapons and manoeuvre capability. The Porphyrion has a solid selection of Secondaries and is able to fill or support gaps in Anti-Tank and Anti-Air should you need it.

Acastus Porphyrion “Tormentor”.

Piloted by Seneschal Hans Jurgen of House Ærthegn

The white elephant in the room in itself is the Warhound Scout Titan, with 590pts for a fully upgraded lascannon and occular augmetic equipped Porphyrion rapidly encroaching on the 750pts a that Titan costs.

For that, you’d get two sets of Str D, AP 2, Primary Weapon 2, Large Blast 5″ at 96″ range if you run twin-turbolaser destructors. So, is that worth the additional 160pts (the price of a casually specified Magos Dominus for a class-above of firepower, defence and manoeuvre)? Yes – it is. However, in Legio Cybernetica or Ordo Reductor armies, which are points hungry, that Warhound Titan might be a snip out of reach and therefore the Porphyrion is the de-facto providing choice for a bit of overbearing firepower.

In short, although not a Titan in lore, scale or firepower, the Acastus Porphyrion is still a titanic weapons system, able to bring overwhelming firepower and increased tactical burden to the mind of an enemy. Just remember to manoeuvre for better target picture taking advantage of the Vehicle (Super-heavy walker) rules, consider threat direction for the ion shield and finally; those important re-rolls granted by twin-linked template weapons.

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