After reading through the rules, I can't find "Enhancement bonus" as a separate and distinct thing when it comes to AC.
Yeah, it's tracked separately for stats because some things count only actual ability mod, not the enhanced one. Int mod to new skills is a clear example of this.
Beyond that, I'm not seeing it.
No, it's not clear. The only quote from the PHB (also in the SRD) that is relevant is "Multiple enhancement bonuses on the same object (in the case of armour or weapons), creature (in the case of natural armour), or ability score do not stack."
This does indeed imply that an enhancement bonus to the mithral shirt and an enhancement bonus to dastana are separate and should stack.
However, as I noted up-thread, the Dastana was updated to 3.5e in Dragon #318, in which James Wyatt (the designer who introduced them to the game) explicitly states that they don't stack (see the relevant post above, which quotes the source directly).
So...
According to some of the arguments presented, my Dastana +4 and my Mithral Chain +2 should pseudo-stack. That is, I'd get the +5 from Chain Mail, the +1 from Dastana, and the +4 Enhancement from the Dastana, but not the +2 enhancement on the chain. And, not to mock anyone, but that sounds crazy.
The reasonin? Dastana have a base +1 that stacks with other armors. The Chain has +5. If the Enhancement bonuses are a separate bonus type and can't stack, I should get the better of the two, right? So 5 + 1 + 4 = 10?
That's how James Wyatt, in Dragon 318, claims it works.
Read even more normally, we'd have +7 (Chain +2) plus 5 (Dastana +4) for a total of +12. And I say "more normally" because Dastana specifically say they stack with other armors.
Yep, that's how Cyclone_Joker has been maintaining it should work. And it is indeed the logical reading.
The problem is that it's an unbalanced combination: it renders the mithral shirt + dastana + chahar-aina far and away the best combination of armour.
I mean, I'm not the top rules expert here, and I freely admit that my book knowledge is far from perfect, but according to everything I can find, "Enhancement" just counts as more points on whatever item is being enhanced, and the stack/no-stack is based on the item or spell in question.
My honest opinion is, frankly, that James Wyatt screwed up when he introduced Chahar-aina and Dastana to the game. His intention was to add two interesting options that would each add a minor bonus to AC. He just didn't foresee the possibility of enhancing all three together to stack for a +15 bonus.
So, having later been presented with this 'hack', he then proceeded to patch it in the worst possible way - by issuing an 'update' rather than official errata, and doing so in Dragon rather than on the WotC website, meaning it had limited exposure, a limited lifespan (since it's now OOP and not legally available online), and of questionable* validity.
* Though Paizo always maintained that their license meant everything they published was 100% official. It was
us who decided that we would exclude their material due to significant balance issues. It would be ironic, then, if this also led to the exclusion of a correction to a clear balance issue!
But I'll note this:
- The only place where this issue appears in the printed rules is in regards to the Dastana and Chahar-aina. In all other cases, there's no problem, since you can't wear two suits of armour together, and armour and shields are separate bonus types that stack together.
- It is very clear from the relevant designer's own words that the intention was that these were
not meant to be enhanced separately and stacked together (Dragon #318 - and note that both the update and Oriental Adventures were penned by James Wyatt).
- Allowing them to stack is problematic, because it renders the mithral shirt + dastana + chahar-aina clearly the best type of armour, breaking the "is this so good everyone will want one?" part of the balance equation. (And note, even, that since such items are all masterwork or mithral, they don't apply any armour check penalty either, so even the "you must have
this armour proficiency to use without penalty" is a non-restriction - even if you don't, you suffer a 'penalty' of -0!)
Also - even if you don't accept the logic that "enhancement bonuses don't stack", if you
do accept the validity of the update from Dragon then that takes care of the problem - since that
does close the loophole with regard to the two items in question. And since the convention is that you should always use the latest sources (that is, you shouldn't use the 3.0e version of an item if a 3.5e equivalent exists) then that really does suggest that the update should be admitted.
In all honesty, though, if I were including these items in my game, I'd make
very sure to add them to my "house rules" document to make absolutely clear how they work - and there, instead of giving a special 'stacking armour bonus' exception, I'd have them just increase the base armour bonus by 1 and explicitly state that they couldn't be further enhanced. But that, of course, is purely in the realm of house rules.
). Deflection bonuses don't stack with deflection bonuses, etc.
