Impact of exploding dammage dice?

[Altin]

I had a thought just recently that an interesting variation on the basic D&D rules would be to have exploding dammage dice. What I mean by that, for those not familiar with the concept, is that when a dammage die rolls its highest value (6 for a d6, 8 for a d8, ect.) it is rerolled and the two values are added together, this being done as many times as the highest value comes up. Other bonuses (strenght, magical argumentation, ect.) would still be added only once.

Now, the idea is probably a little too outlandish to use in most campaigns I can think of and it would probably play havoc with the magical weapon pricing system but - just theoretically - what would be some of the gameplay consequences? For instance:

I imagine simple duke-it-out combat would get even deadlier at low levels and would stay deadly for a bit longer than it does with the normal rules.

At least in theory, a single lucky blow could kill just about anyone (but the better they were, the luckier it would have to be) which adds a bit more realism to proceedings (whether this is a positive thing or not I will leave as an exercise for the reader).

The symptom of other bonuses making the die roll more or less irrelevant at higher levels would be aleviated slightly as exploding dice would mount up significant dammage now and again.

Weapons which use dice with lower ranges would become more desirable in comparison to their high-range counterparts (ie. a d6 would explode more often than a d8). In other words, the ranger with two shortswords would become even more disgusting .

The last is potentially the most problematic change but, according to my maths, a dagger (which explodes 25 % of the time) still sucks in comparison with a longsword (explodes 12.5 % of the time). For instance, in eight hits, a dagger will on average do 6d4 normal and 8 (two max rolls) + 2d4 exploding dammage without factoring in repeated explosions. A longsword, by comparsion will do 7d8 normal + 8 + 1d8 exploding dammage. Thus:

Dagger = 8 + 6d4 + 2d4 = 8 + 8d4 = 28 dammage on average whereas
Long Sword = 8 + 7d8 + 1d8 = 8 + 8d8 = 44 dammage.

A d6 to d8 comparison is somewhat more complicated as the first common denominator is 24 but, if my maths is right the numbers look like this (note that not including repeated explosions is a bigger distortion because of the increased sample size but this is much simpler to work out):

Short Sword = 24 (4d6 each rolling a six) + 20d6 + 4d6 = 24 + 24d6 = 108 dmg
Long Sword = 24 (3d8 each rolling an eight) + 21d8 + 3d8 = 24 + 24d8 = 132 dmg

It has just occured to me that the 'normal' dammage should be calculated with the assumption that the maximum will not be rolled (ie. a non-exploding d4 should return results in the range from 1 to 3, not 1 to 4) so the average results I used for the above calculations should be slightly lower. Still, I think this actually favours weapons with greater rangers and should in any case not change the results too drastically.

So, what do you think? Are there any other consequences of the change that I'm not seeing? Any game-breakers this would cause?

Yours,
Altin

 

[Jens]

Damages will potentially be higher, making attacks a little more dangerous. Having played Earthdawn where pretty much all rolls are done like this, I can tell you that you should expect increased randomness and more casualties (What?! 42 on a d10??)

By the way, you can get the average damage A of rolling a dN by solving this for A:

A = [N*(N-1)/2]/N + (N+A)/N

To understand the equation, note that N*(N-1)/2 is the sum of 1+...+(N-1).

 

[Thorvald Kviksverd]

Hackmaster does something very similar, and it gives an extra 20HPs to most characters and monsters by way of compensation. In the spirit of d20, you could instead use CON, CON + STR MOD, or something similar.

 

[pontus]

And here I was hoping this would be a thread about dice exploding and maiming players.

 

[Xeriar]

Most games with all-exploding dice don't have spells though... as each explosian counts as a bonus caster level that isn't capped by the spell.

Also, though it may look like it, lower dice grades are not more favorable. A d4 has a 1 in 16 chance of breaking 8, while a d8 has a 1 in 8 chance. It has a 1 in 256 chance of breaking 16, while a d8 has a 1 in 64 chance, etc...

Freak incidents are fun, I once rolled 92 points for armor peircing arrow damage in Legend of the Five Rings. Considering that that would drop Hida Kisada (my character had an ancestor that ignored damage reduction abilities) to 'down', that is -not- shabby.

But, IMO, if you want realism, there are far better systems than d20 for that.

 

[fuindordm]

It's actually not as complicated as it sounds. I studied this issue once (for Earthdawn, I think) and when you work out the math an exploding die does 0.5 more on average than a regular die, regardless of the size. So an exploding d4 averages to 3 instead of 2.5, an exploding d6 averages to 4 instead of 3.5, and so on.

This means that weapons with multiple dice are favored over those with single dice; this perhaps gives a needed boost to the polearms. A 2d4 weapon averages 6, which is not bad at all compared to a 1d10 weapon averaging 6.5.

If you don't want to change the game too much at first, but do want a little cinematic feel, I suggest the following:

1) allow weapon dice to explode, but not bonus dice such as flame or sneak attacks.
2) to compensate for the greater damage that players will be receiving, allow them the best of two rolls at each level for HP. This also makes the average difference between different sizes of hit dice 1.5 HP instead of 1 HP.
3) to keep the greatsword from being the obvious best choice of weapon, maybe make it a d12 instead of 2d6.

If you want to place limits on the amount of damage small weapons can do, you can implement the Hackmaster rule that each additional die rolled gets a -1. So someone who rolled 4, 4, 2 with a dagger does 4+(4-1) + (2-2) = 7 damage. I don't know how this would affect the average damage though.

Have fun!
--Ben

 

[gpetruc]

If you want a little math:
the average of an exploding dice with n faces is, as Jens said:
avg = 0.5 * (n+1) n / (n-1)
that is exactly 0.5 * (n+1)/(n-1) more than the standard dice
And so the avgs :
d2 = d3 = 3
d4 = 3.33 (normal d4 + 0.83)
d6 = 4.20 (normal d6+0.70)
d8 = 5.14 (... +0.64)
d10 = 6.11 (... +0.61)
d12 = 7.09 (... +0.59)
d20 = 11.05 (... +0.55)
d100 = 51.01 (... + 0.51)

If you subtract 1 to every dice after the first the equation becomes:
A = [N*(N-1)/2]/N + (N+A -1)/N
that has the solution
A = N/2 + 1
and this is exactly the average of the normal dice + 0.5.

Of course if you have a weapon that does more than one dice of damage, simply multiply the average damage for the number of dice

 

[Cloudgatherer]

I think this would be very difficult to integrate into D&D. The system just isn't set up for it. Melee combat is one thing, but fireball becomes a super powerful spell when a bunch of those 10d6 start "exploding".

I recently started playing Hell on Earth, which uses such a system. The number of dice one rolls is reduced by quite a bit (plus it is a skill based, not class based, system). There is a d20 version of HoE, I wonder how they handle it....

 

[Plane Sailing]

What would you do for critical hits? Would you allow each of the dice rolled for the critical potentially "explode"? If so, the axes, spears and picks etc. are likely to become even more fearsome in the advent of a critical.

Just pointing this out since I don't think you'd mentioned the possibility.

Cheers

 

[Atma]

Ok...

how are you going to handle things like shurikens, which deal a flat 1 point of damage..