40k - Ork Mob Rule vs Psychic Shriek

Question

I think I know the answer to this but was just hoping someone could prove me wrong... Let's say you're casting Psychic Shriek against a mob of 15 Boyz. Psychic Shriek states "Roll 3d6 and subtract the target's leadership," while Mob Rule states "...may always choose to substitute the number of Orks in their mob for their normal Leadership value." Do you roll the 3d6 against their Ld value of 7 (for Boyz), or can they choose (per the mob rule) to substitute Ld 10 for this? It's not a Ld test, nor does it require any intervention by the Ork player which might give them an opportunity to decide to substitute it, but the wording of mob rule is just vague enough that it seems they can do it, literally, whenever they want.

The counter-example is that they should be able to do it whenever their intervention is required, such as for a morale/pinning test, but not when something is comparing to their base leadership stat. I know that's pretty weak, but it holds just enough logic that I feel clarification is in order.

BONUS QUESTION: Does Mob Rule still apply to a character in a challenge? Granted I've heard rumors that the new codex will make Orks immune to challenges but figured I'd ask anyways.

Answer 1

In the Letter of the Law:
Psychic Shriek asks you to evaluate the target unit's Leadership value. It does not say that it causes them to make a leadership test, so it can still apply to things that ignore/auto-pass leadership tests.

Ork Mob Rule says you (meaning the Ork player) may always choose to substitute the number of Orks in the mob for their Leadership value. It does not have a limitation of when this can be done (so technically, randomly in the middle of the shooting phase, you can just declare "oh, and because there's 9 of them left, their leadership is 9").

In the Spirit of the Law:
Orks are either so dumb they don't know they should be afraid of things even if they out number them, or so incredibly brilliant and powerful that we mere 'umies are unable to comprehend their courage. This invigoration seems to come from a quick head-count of their numbers and the raw logic that US > THEM == VICTORY. So when attempting to scare the spores out of a group of Orks, you have to consider that either they get a little scared, but after looking around for help find themselves in sufficient quantity to handle the threat, or they realize they are confident in the prowess and abilities of their compatriots and simply dismiss the threat.

Answer 2

6th Edition

You are correct in your interpretation: the target's leadership is determined by the Mob Rule special rule.

Ork Psychology and morale is directly linked to the number of Boyz around them at any given time. ... Ork mobs may always choose to substitute the number of Orks in their mob for their normal Leadership value.

Mob Rule! is in effect at all times, regardless of whose turn or what action is requesting the leadership value. Thus, 15 Ork Boyz means subtracting 15 from the 3d6 that the Psychic Shriek-attacking player rolls.

This is in line with the answer provided by @DavidCEllis.

To answer your bonus question, while the challengers may be separate from the assault in terms of wound allocation, they are still very much part of the unit/mob they entered the assault with. Therefore, the character in the challenge as well as the accompanying unit can use the Leadership value Mob Rule! bestows.

Rule-as-Written vs Rule-as-...Expected

Contrary to the BRB (6th and 7th), this answer asserts that leadership may exceed the normal 10:

All but one of the characteristics are rated on a scale from 0 to 10.

This seems to be commonly held as an unbreakable rule, and indeed forums about this at large does seem to interpret the rule with a hard capped 10. In support of this, the Ork FAQ for 6th edition actually partially addresses this:

Can a Weirdboyz leadership be increased to more than 10 by Mob Rule?

A. No, it can be increased, but only up to a maximum of 10.

Much to my dismay, however, we will find this rule almost impossible to reference for current play. GW has discontinued distribution of 6th edition FAQs to replace it with the 7th edition FAQ, where this rule is woefully absent.

In light its (deliberate? accidental?) removal from the FAQ, the rule from the BRB (again 6th and 7th) iterates:

On rare occasions, a conflict will arise between a rule in this rulebook, and one printed in a codex. Where this occurs, the rule printed in the codex or Army List Entry always takes precedence

It seems like GW could have easily cleared this up by adding to Mob Rule in the FAQ "to a limit of 10 LD" (even in the FAQ they directed this only to Weirdboyz) or by saying "superseding the normal limit of 10 LD" or any variety of phrasings... but RAW, they didn't.

This is likely to be a hugely unpopular interpretation, and thus most players (non-Ork, Ork?) may amicably decide that LD10 is the cap, which is fine and the intended way for rule conflicts to be resolved. That said, in 6th I'd say it's perfectly viable to do a roll-off for rule interpretation.

7th Edition

If every model in a unit has this special rule, and the unit fails a Morale check or Pinning test (after any re-rolls they may have), roll immediately on the following table:

The flavourful leadership boon is entirely gone, replaced with a d6 roll table, and it's pretty straightforward.