Do LETHAL HITS and DEVASTATING WOUNDS stack in 40k?
Short answer: no, not on the same attack. LETHAL HITS skips the wound roll, and DEVASTATING WOUNDS needs a wound roll to trigger on. Take the auto-wound and you have given up the chance of mortal wounds from that attack.
A weapon can carry both abilities, and across a full volley both will matter. But for any single attack you get one or the other, never both.
Why they cannot both apply
The two abilities sit at different points in the attack sequence, and the first one closes the door on the second.
LETHAL HITSacts on the hit roll. A critical hit automatically wounds, which means the attack moves straight past the wound roll.DEVASTATING WOUNDSacts on the wound roll. A critical wound inflicts mortal wounds instead of a normal wound.
If an attack never makes a wound roll, it can never produce a critical wound. So an attack that auto-wounds through LETHAL HITS is not eligible for DEVASTATING WOUNDS, no matter what else is going on.
Does LETHAL HITS trigger DEVASTATING WOUNDS?
No. This trips people up because both abilities key off a critical roll, so it feels like one should feed the other.
They key off different rolls. LETHAL HITS responds to a critical hit. DEVASTATING WOUNDS responds to a critical wound. An auto-wound handed to you by LETHAL HITS is a successful wound, not a critical one, so there is nothing for DEVASTATING WOUNDS to fire on.
What is the difference between the two?
They solve different problems:
LETHAL HITSsaves you a roll. It converts a critical hit into a wound, so you skip the risk of failing to wound. It does nothing about the target's save.DEVASTATING WOUNDSbypasses the save. It converts a critical wound into mortal wounds, which the target does not get to save against.
That difference is what makes the choice interesting. Against a target you struggle to wound, skipping the wound roll is worth a lot. Against a target with a strong save, getting past the save is worth more.
What changed in 11th Edition
In 11th Edition, LETHAL HITS became optional. You can choose to have a critical hit automatically wound, rather than being forced to.
That single word is what creates the decision. Under a rule that forced the auto-wound, a weapon with both abilities would never get to use DEVASTATING WOUNDS off a critical hit. Being able to decline the auto-wound means you can roll to wound instead and keep the mortal wound chance alive.
So which should you take?
It depends on two things: what you need to wound, and how often the target fails its save.
Taking the auto-wound gives you a wound for certain, which the target then gets to save against. Rolling risks failing to wound, but a 6 to wound is a critical wound and skips the save entirely. Rolling only comes out ahead when the target's save is good enough that the odd mortal wound is worth more than the wounds you lose by rolling.
A rule of thumb: roll if the target fails its save less often than 1 time in N, where N is the number you need to wound.
| You wound on | Roll instead if the target fails its save less than |
|---|---|
| 2+ | half the time (a 3+ save or better, after AP) |
| 3+ | a third of the time (a 2+ save, after AP) |
| 4+ | a quarter of the time (a 2+ save with no AP against it) |
| 5+ | a fifth of the time (a 2+ save with no AP against it) |
| 6+ | never, take the auto-wound |
So against most targets the auto-wound is the right call. Rolling pays off when you wound easily into heavy armour.
A few other things shift the balance:
- Re-rolls and +1 to wound favour rolling, since they cut down the wounds you lose.
- A
Feel No Painagainst all damage hits both options equally, so it changes nothing. - A
Feel No Painthat only works against mortal wounds favours the auto-wound.
How UnitCrunch handles it
When a weapon has both abilities, UnitCrunch makes the choice for every critical hit the way a player would: it works out how much damage each option gets through on average and takes the better one. It counts what you need to wound, wound roll modifiers and re-rolls, the target's save, AP, invulnerable save and Feel No Pain. When the two come out exactly level, it takes the auto-wound.
In a unit with mixed saves, it checks the save of the models each wound is likely to land on. The first few wounds of a volley are weighed against the models first in line. Once enough wounds have been dealt to get through them on average, later wounds are weighed against the models behind. So a volley into a squad led by a character in heavy armour can take the auto-wound early on and start rolling once the squad is expected to be gone.
Two worked examples
A weapon with Strength 8 attacking Toughness 4 wounds on 2+. Against a 2+ save with no AP:
- Taking the auto-wound, 1 in 6 critical hits gets through the save, about 17%.
- Rolling, 4 in 6 are normal wounds that get through 1 time in 6, and 1 in 6 is a critical wound that skips the save. That is about 28%, so UnitCrunch rolls.
A weapon with Strength 4 and AP -1 attacking Toughness 4 wounds on 4+. Against a 3+ save, which fails half the time after AP:
- Taking the auto-wound, half the critical hits get through, 50%.
- Rolling, 2 in 6 are normal wounds that get through half the time, and 1 in 6 is a critical wound. That is about 33%, so UnitCrunch takes the auto-wound.
If you want to model the other choice instead, set the weapon up without DEVASTATING WOUNDS, or without LETHAL HITS, and compare the two results side by side.