What are the rules on stacking magical abilities for weapons

[Patryn of Elvenshae]

Could you give a specific reference on that? It's counter to the way I'd always interpreted it.

No, unfortunately, I cannot. I don't recall the module in which it appeared.

As far as rules that disallow it, it's generally prohibited when you randomly generate items, and certain abilities have language such that they don't stack with each other, but that's the only place it appears.

2 Reroll if you get a duplicate special ability, an ability incompatible with an ability that you’ve already rolled, or if the extra ability puts you over the +10 limit. A weapon’s enhancement bonus and special ability bonus equivalents can’t total more than +10.

...

Keen: ... This benefit doesn’t stack with any other effect that expands the threat range of a weapon (such as the keen edge spell or the Improved Critical feat).

Generally speaking, 2d6 fire tends to be less mechanically sound than 1d6 Fire + 1d6 Cold (etc.), because of the way Energy Resistance / Immunity tends to work.

 

[Pyrex]

With Brilliant Energy going through natural armor and armor, you'd only have to stay alive for 6 rounds, which many people can do.
WOUNDING
(CON=0 DEAD)

Ignoring for a moment the debate about adding properties more than once, Brilliant only ignores Armor and Shield bonuses. It does not ignore Natural Armor.

Brilliant Energy is (IMO) pretty much the worst enhancement in the book. (but that's another thread...)

 

[Drowbane]

The only real question I'd have with that is, how does that interact with Fire Resistance? Is each of those extra dice resisted separately? For example, Bob has Fire Resistance 5, and Sam stabs him with a +1 flaming flaming dagger. Sam rolls a 4 and 6 on his two dice of fire damage. Does Bob take 5 points of fire damage (add the 6 and 4 and then apply fire resistance), or 1 point of fire damage (apply fire resistance to each die)?

Assuming you rolled max dmg with a +1 Flaming Dagger vs someone with Fire Resistance 5...

Piercing damage: 5
Fire Damage: 1

Now if they had Fire Resist 5 and DR 5 / -...

Piercing: 0
Fire: 1

 

[Deset Gled]

No, unfortunately, I cannot. I don't recall the module in which it appeared.

As far as rules that disallow it, it's generally prohibited when you randomly generate items, and certain abilities have language such that they don't stack with each other, but that's the only place it appears.

IDHTBIFOM, but I seem to remember this being disalowed in 3.0. I also remember a couple of old threads on the topic. Maybe someone (who has a paid account and isn't at work) could look up either of these and find where the 3.5 wordage differs?

Personally, I wouldn't allow it. I think it sets a bad precedent that can be exploited in many situations (Crosshairs wounding example for one, the idea of multiple Keens being another).

 

[Patryn of Elvenshae]

Personally, I wouldn't allow it. I think it sets a bad precedent that can be exploited in many situations (Crosshairs wounding example for one, the idea of multiple Keens being another).

You did notice that Keen is one of the rules texts I quoted to show abilities that wouldn't stack when used more then once?

 

[Deset Gled]

You did notice that Keen is one of the rules texts I quoted to show abilities that wouldn't stack when used more then once?

The text you quoted states that Keen doesn't stack with "any other effect" that increases threat range. This is a case of it stacking with itself.

And, now that I sit back and think about it, the inability of any property to stack with itself unless stated otherwise is exactly the reasoning I would use to explicitly disallow multiple enchantments of the same type (and was probable the 3.0 ruling I was remembering).

 

[Infiniti2000]

It's not any "property", it's any "effect." Damage, however, always stacks. So, 1d6 fire stacks with any other 1d6 fire. The keen effect, however, does not stack with keen effects and specifically not with any other similar ability.

 

[Nail]

Moreover (IIRC), when I've run the numbers of average damage per round, etc.....letting the energy enhancements stack (x3 flaming, etc.) is No Big Deal(tm). Seriously.

If you'd like, I'll post the numbers.

 

[IcyCool]

Moreover (IIRC), when I've run the numbers of average damage per round, etc.....letting the energy enhancements stack (x3 flaming, etc.) is No Big Deal(tm). Seriously.

If you'd like, I'll post the numbers.

Did you factor Energy Resistance into that (i.e., against each die, and against stacked dice)?

 

[Nail]

Did you factor Energy Resistance into that (i.e., against each die, and against stacked dice)?

As a part of the final summary, rather than within the math. That's because the prevalence of energy resistance is so campaign specific.