"Ability" has a technical meaning in Descent.  So you're suggesting that "this ability", rather than meaning "Ironskin, the ability we're talking about", actually means "the effect described in the last sentence" (which is not, technically, an "ability").

I'll admit the Descent rules are rampant with sloppy wording errors, but I think that's quite a stretch.  Especially since there were arguments on the forum before SoB came out about whether a Ironskin could make a hero immune to part of an avatar's attacks under the "no immunity" rule, and so that sentence is timely under the common interpretation, while being entirely redundant with the existing general "rule" under your interpretation.  (Well, probably.  The "no immunity to avatars" rule is extremely vague and sounds to me more like some designer saying "fix it yourself".)

I'm also not aware of any previous case where they have explicitly isolated one part of an ability to write additional rules for it.  It's conceivable I'm mistaken, but I'm pretty sure that's totally unprecedented in Descent.  So you're suggesting that the first and only time they decide to do this, they screw up the wording.

Ispher said:

The reason for using "this ability" instead of a 4th iteration of "Ironskin" in less than 50 words is to avoid the reader trailing off in mind-numbing boredom. Clearly the FFG rules editors are not logic-mongers, they are authors. Good authors know that one of the fastest ways to turn your audience off and have them walk away is to use the same word over and over again when a synonym or similar phrase will get the same message across. A paragraph that should be clear on the very first read through becomes confusing when multiple uses of the same word cause each sentence to blur into the others in the mind of the typical reader. Unfortunately this artistic flair sometimes bumps heads with the teeming masses of anal retentive rules lawyers looking to eke out any advantage they can.

Antistone pointed out the logistics of the phrase much better than I could, but you are of course free to request it be added to the FAQ. I personally hope it doesn't get put in, as the FAQ is already bloated enough and "a guy asked a question" doesn't seem to match up with a "frequently asked questions" document.

Antistone said:

Well, "ability" is used in a variety of ways in the SoB rulebook: avatar characteristics are coined as abilities (on p.7, "The Pack" is defined as the Avatar's Special Ability), hero characteristics are coined as abilities (on p. 10, the rules inform about changes to Sir Valadir and Runewitch Astarra's abilities), on p. 39 there is a list of "Advanced Campaign Special Abilities", and the way the heroes are able to move on the map is also coined as an ability (p. 8: "The party begins with the ability to travel along normal and ocean trails")... So if you know the "technical meaning" of  "ability" in Descent, I'd be glad to read it.

Nitpicking aside, I noticed that "This ability" is often used in the last sentence of some Advanced Campaign Special Abilities (like Blast, Bolt and Breath), and that it always refers to the whole ability. So for coherence reasons, "This ability" in the Ironskin rules must indeed refer to Ironskin. Taken out of context however, it wasn't that clear, not to me at least. Sorry for the fuss.

James McMurray said:

While it is well-established in prose that unnecessarily repeating the same word or phrase is a bad idea, it is also well-established in technical writing that using several different words or phrases to refer to the same object or concept (especially new phrases that you make up as you go along) is an even worse idea. 

Your guess at the reason they didn't is plausible and understandable, but not a justification.  They SHOULD have said "Ironskin" again there.  No question.

I have a related question about Ironskin as described in the Final FAQ's under the heading "Sorcery Vs. Ironskin."

I think I'm reading too much into it.  After reading the following:

"Sorcery versus Ironskin
Sorcery may not add damage to any attack that includes a figure with Ironskin. It may add range to the attack, but not damage. Yes, Laurel can get around this. The damage immunity granted by Ironskin does extend to all figures affected by an attack that includes a figure with Ironskin. This refers solely to the damage caused by the Sorcery skill."

If the damage immunity given by ironskin would protect all figures in an area attack that included a figure with ironskin, then does the "all damage dealt
to figures with Ironskin by attacks that affect more than one space (such as Blast, Burn, and Breath) is reduced to zero" protect the other figures as well by reducing the entire attack damage to 0 i.e. can the figure with ironskin stand in the middle of the party and act as a shield against dragon breath? 

Or would the other (non-ironskin) figures take full rolled damage from the area attack and only the figure with ironskin would have the attacks damage reduced to 0?

I thank you for any clarification, as do my players.

TwistedCricket42 said:

Any damage added by Sorcery to an attack that affects any figures with Ironskin is reduced to zero (immune).

It is explicitly only this (Sorcery) damage that is reduced to zero for all figures

Example:
An attack does 8 normal and 2 sorcery damage, and affects 3 figures with (i) Armour 2, (ii) Armour 3 and (iii) Armour 4 and ironskin.
(i) suffers 6 wounds (8D-2A=6) as all the sorcery damage is removed due to (iii)'s ironskin
(ii) suffers 5 wounds (8D-3A=6) as all the sorcery damage is removed due to (iii)'s ironskin
(iii) suffers 0 wounds as it is an AoE attack affecting more than one figure.


PS. This place is pretty much dead. BGG is the place to go for questions now.

Dead of not, thank you for the informative replies.