N18 Promethium Tank Refuelling Station terrain (how to not write rules)


Hive Lord
Dec 29, 2017
More rules for terrain that explodes! Some really weird stuff here. This is yet another terrain with special rules for how it explodes (amont other things). Similar to Promethium Cache, Promethium Pipes and countless scenario special rules for stuff that goes boom.

Whenever a Promethium Tank is hit by a ranged or close combat attack, roll a D6 and add the attacking weapon's Strength. On a 9+, the tank's iron casing has been pierced and unleashed a jet of gas. Centre the 5" Blast on the part of the tank closest to the attacker. Any fighter touched by the marker must pass an Initiative check or become blinded just as if they were hit by a weapon with the Flash trait. If the weapon that hit the tank has the Blaze trait, any fighter touched by the marker must pass an Initiative check or suffer a hit from a flamer instead.

It took me 10 seconds to understand how unintuitive this can be.

1) Blue throws an indcendiary grenade next to the promethium tank:

2) The blast hits the fighter and the tank

3) when the tank is hit, another explosion triggers "closest to the attacker"

What happens now? The fighter is hit by the original attack. The vehicle is not hit because the tank only affects fighters!?! Why is that distinction valuable? Depending on the attacker's weapon, it will either be Blaze or Flash, both of which by default affects models (vheicles and fighters), but the tank limits this to only affects fighters.
Somehow, reading their rules I suspect they wrote it with linear attacks in mind.
The grenade seems to be an exception to this as the direction of the “attack on the tank” would be from the grenade’s blast, not the attacker?

But even if we go with RAW and your diagram, it’d be odd that a blast that hit any object would’t trigger that object, in this case a vehicle.

What if that second blast hit a second promethium tank? Or anything that might be affected by blaze?
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We think alike :giggle: Yes I'm willing to accept that shockwaves from the initial hit/blast could transfer the high pressure gas explosion to another location. Or if very imaginative, the grenade could bounce of one side (where the tank's explosion triggers), then scatter and bounce to where it actually ends up.

It is as you say weird that explosion from the tank affects fighters but not vehicles. However in this case it could be argued for that GW actually thought about and prevented the case of chain blasts to multiple tanks. Because other rules for when it actually explodes completely (and is subsequently removed from the battlefield), it specifies:
When a Promethium Tank loses its last Wound, it may explode with devastating consequences! The player that caused the last Wound to be lost rolls a D6 - on a 3+ the Promethium Tank explodes! All models (including other Promethium Tanks) belonging to both players within 3" of the exploding Promethium Tank suffer a S4, AP-1, D1 hit as if from a weapon with the Blaze trait. The Promethium Tank is then removed from the battlefield.
So destroying it could cause a chain explosion across other tanks. This is not specified for the minor explosion when hit, so arguably chain hits doesn't apply there. Or another solution they copy-pasted some N19 Badzone terrain rules for similar promethium terrain, updated parts of it to accommodate the N22 rules (including vehicles) but forgot to update other parts.

In my mind it is more cumbersome to remember this distinction that for some attacks to affect both vehicles and fighters, and some to only affect fighters.
Ok, so that makes sense that that have a bigger rule for full on explosions.

But this is the game where through the power of prayer or a tactics card an entire 1’ square of table can spontaneously combust - so chain explosions is nothing really!! 😂

Reading this “the tank's iron casing has been pierced and unleashed a jet of gas” makes me wish they’d used the flamer template from the point of impact instead!
Yeah sounds like a flame template, but how to even start writing rules on how to place that! When checking closer it turns out several parts of the rules for this terrain was lifted from the spectacular terrain rules from 2019. High Pressure Gas, Fuel Slicks and Free fuel.
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Yeah sounds like a flame template, but how to even start writing rules on how to place that!
Draw a line towards the attacker/center of the blast and fully allign a flame template alongside it.

As for the weirdness of explosion not hitting the vehicle itself, they probably did it to be less lethal to the vehicle, otherwise even autoguns could stunlock the driver due to flash trait.
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The Gunk Tank in Book of the Outcast has a similar rule but when it's punctured the 5" blast is centred on "the point that was hit". I have to wonder if "part of the tank closest to the attacker" was an attempt to answer where the point that would be hit is, without considering the ramifications of that answer.
Must be an opportunity to put a scatter dice into the solution somewhere. Use @JawRippa suggestion on initial template placement then have there be a roll for the next turn, say 3+ for another template blast with the scatter indicating where the template moves to. If the template scatters back through the tank have it explode. In the spirit of true capitalism have the number of turns for randomized template continuance be tied to the number of promethium tank kits used in the terrain piece. Two kits? Roll for another turn of randomized mayhem after the first, etc. etc.