Saturday, January 22, 2011

Boon of Mutation vs. Soul Devourer

The ability to turn enemy combatants in to jibbering chaos spawn must be one of the most annoying (for the enemy) and fun (for the chaos player) ability that there is.

I've been thinking about Boon of Mutation in relation to Heralds of Tzeentch as a defensive measure.  The main choice as a defensive measure is either the Boon of Mutation, or the Soul Devourer (power weapon with a Ld test imposed for each unsaved wound that can cause instant death).  Which is better though?

The Boon has a 3+ chance of hitting (conducted during the shooting phase, even if the herald and target are engaged in combat!), and then the target needs to pass a Toughness test.  Let's assume for the moment that the target has T=4.  This means a 5+ is required to turn the target in to a chaos spawn.  Hence the probability is 0.22 for success (or 1 in 4.5).  This takes care of the target full stop - no invulnerable (or other) saves apply as no wounds have been caused.  In contrast, for soul devourer, the Herald will get 4 attacks during the combat phase (assuming it is on a chariot for the moment) and will hit of 4+ (against WS=4) and wound on 5+.  That means a 1 in 6 chance of a power weapon wound per attack, or a total of 0.67 unsaved wounds per combat round.  Against Ld=10, there will be a chance of 0.05583 (about 1 in 18 chance) of the target getting its soul devoured if it has more than one wound.

That needs some interpretation though.  Against space marines, the soul devourer is going to hurt regular marines most turns.  Except for commanders and those other miniatures that possess invulnerable saves, of course.  It could make regular squads think twice before charging in ... but what do terminators with a 3+ invulnerable save care?  Probably very little.  Moreover, the chances of inflicting instant death against a pesky three wound space marine character with an invulnerable save is incredibly slim.  A quick analysis shows that the herald stands the same chance of turning a 3+ invulnerable save terminator in to a spawn as causing a wound with a power weapon from 4 attacks! (i.e. the probability of killing a regular storm shield terminator with a power weapon is 0.22 for the herald!).  But with Boon of Mutation, if it is successful, not only does the herald kill the terminator, the team also gains a chaos spawn miniature.

But when faced with a T=3 Dark Eldar Archon (or Lelith Hesperax even), the herald has a probability of 0.33 (1 in 3 chance) of working per turn.  That's got to be worth considering given that the herald may not survive a several rounds of combat with Lelith (etc.).  Combined with some other powers, it could be an effective block against webway incursions.

Here's one such build:
Herald of Tzeentch with Chariot, Bolt of Tzeentch, Daemonic Gaze, Boon of Mutation and Master of Sorcery -- 130 points.

With 2 or 4 of them on the field, they could be very efficient at producing a chaos spawn per turn, or pummelling down multi-wound characters if that fails.  I know that others may consider Breath of Chaos better value that the Boon for the same amount of points (in all likelihood it is!), but Boon of Mutation is much more satisfying in its own chaotic way and can be used defensively whilst in combat, unlike Breath.

Finally, I'll note that the chaos space marine Gift of Chaos psychic ability (same thing as Boon of Mutation, but a different name) and the daemons version is worded slightly differently.  If the target is hit, they must make a toughness test immediately or be turned in to a spawn, but in the chaos space marine version, a roll of a 6 is explicitly noted as always being a failure, but the daemons ability is not.  It is worth noting that on page 8 of the 40k rulebook, it explicitly notes that all rolls of a 6 on a characteristic test always fail.  Therefore there is no difference between Gift and Boon in this regard, despite the different wording. Hence both of them have a chance even against Mawlocks (etc.).  


Aleksi Lehtio said...

Does the Daemons entry say to take a toughness test. I think the BRB says that a 6 on characteristics checks always fails. Not sure though. Interesting thoughts about boon.

jabberjabber said...

Hi Aleksi -- You're absolutely right. A roll of a 6 is noted as always being a failure on page 8 of the rulebook. I've modified the wording of the post accordingly! Thanks for the comment :)

AbusePuppy said...

The secret answer is that neither of them is really very useful against MEQs and such, although Soul Devourer is useful against Tyranids, Orks, and other armies which have very limited numbers of EW models and mediocre leadership.

jabberjabber said...

I tend to agree with you Abuse Puppy. Tzeentch heralds just shouldn't be in close combat, period. But I have been toying with the idea of a Tzeentch army with at least 6 models with Boon... just for fun!

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