Is Iaijutsu Focus bonus damage subject to double damage? Or triple?

I am a fan of the Iajutsu Master. Though I've never really been a fan of charging builds, I recently saw the weapon enhancement Valorous from Unapproachable East which does double damage on a charge and it got me thinking.

Is there any game mechanic that would double Iajutsu Focus damage? Remember, it is not sneak attack damage, it is not precision based damage or skirmish damage. It is pure bonus damage based on the uncanny speed of the strike.

I have not played since 2010 but I used to play Iaijutsu Masters as a favorite class and I never once made any attempt to try to double the IF bonus damage. Perhaps there is a ruling out there somewhere which prohibits it (and I simply forgot)?

The rules for multiplying damage are pretty clear:

Multiplying Damage

Sometimes you multiply damage by some factor, such as on a critical hit. Roll the damage (with all modifiers) multiple times and total the results. Note: When you multiply damage more than once, each multiplier works off the original, unmultiplied damage.

Exception: Extra damage dice over and above a weapon’s normal damage are never multiplied.

These rules cover any damage multiplication, critical hit or otherwise, and exempt any form of bonus damage dice, sneak attack or otherwise.

So no, Iaijutsu Focus damage dice are not multiplied in any circumstance. However, the iaijutsu master prestige class includes the strike from the void feature at 5th level, which adds his Charisma bonus for each die Iaijutsu Focus adds to his damage. That flat damage would be multiplied on a critical hit or in other circumstances that result in damage multiplication. Also, notably, since the bonus from Charisma, even applied multiple times, is a bonus to the damage, not the damage itself, it would be multiplied as in normal mathematics, not by adding multipliers.

That is, if a 5th-level iaijutsu master makes an Iaijutsu Focus check to add three damage dice and has Strength 20 and Charisma 16, for example, his damage bonus would be

$$+5_{Str} +3\text{d}6_{\text{Iaijutsu Focus}} +3_{Cha} +3_{Cha} +3_{Cha} \\ = 14+3\text{d}6$$

If this damage is doubled, it would be

$$\left[+5_{Str} +3\text{d}6_{\text{Iaijutsu Focus}} +3_{Cha} +3_{Cha} +3_{Cha}\right]\times2 \\ = +10_{2\times Str} +3\text{d}6_{\text{Iaijutsu Focus}} +6_{2\times Cha} +6_{2\times Cha} +6_{2\times Cha} \\ = 28 + 3\text{d}6$$

Rather than simply taking the $3 \times Cha$ of the original an adding another multiplier for $4 \times Cha$.

• Ah, there you have it! That's why I never tried to multiply IF bonus damage. However, on the multiplying of the extra damage, I can see where you are coming from, but I believe you are mistaken. The 5th level Iaijutsu Master class ability: Strike from the Void (Ex): An iaijutsu master of 5th level or higher adds her Charisma modifier to each extra damage die gained from using the Iaijutsu Focus skill. – Aceon Sep 20 '16 at 2:33
• Therefore if you add Cha to each extra bonus damage dice, then it can NOT be considered base damage and thus not subject to any multiplications, as it is added to each bonus damage dice and as you pointed out - bonus damage dice are never multiplied. – Aceon Sep 20 '16 at 2:36
• @Aceon Hmm. That’s a very good point, but I think it could be read either way. That would have to be a DM ruling, I think. I’ll update my answer when I get a chance. – KRyan Sep 20 '16 at 13:30