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Twin Cities Roleplaying Association Message Board TCRA Main Forum › Alternates to d20

Alternates to d20

Troy S.
SkullThrone
Minneapolis, MN
Post #: 42
I'm just throwing this out there wondering if anyone has found a got alternate to d20 that is more dice pool like. We just got done playing a Pathfinder game where we joked about this every time we rolled a d20, we followed it up with a 2d10 roll adding the results for the roll.

What this does is provide a greater probability of getting mid rand numbers 70% of the rolls lie between 7 and 15, with nearly 30% of this being 10, 11 or 12. With only a 1% of a 2 (no ones allowed) or 1% for a 20. A 6 and a 16 both have 5%, and 2-5 or 17-20 only occur 10% of the time.

This seems to give a greater pay off for bonuses, and thus things like improved init payoff more often, as most rolls group around the average.

An interesting "crit" idea came up where rolling doubles is a "crit", which you have a 10% chance to do, but if you now require the double to also hit, than that determines whether the roll is a "crit success" (a.k.a. Nat-20) or a "crit-fail" (a.k.a Nat-1). This leaves things like double 6's being sort of scary, because they might be a crit-success on some creature, with a low AC, or on a well armored opponent you may need double 8's or better to crit-success.

Anyway, we joked all throughout our session, and just wondering if anyone has tried to replace the d20 with something else...without having to totally re-write the game mechanics...which it seems like d10+d10 would allow.
William C.
user 43358752
Eden Prairie, MN
Post #: 12
The problem I see with that is most targets (DCs and ACs) are balanced to require an above-average roll to hit or overcome, and the probabilities of 2d10 rolls makes the percent chance of hitting those numbers less. Since physical attacks require a to-Hit roll on the part of the attacker, while most spells and powers require a Save on the part of the defender (and Touch Attacks ACs are typically rather low), it could very well skew the power more in favor of spellcasters and manifestors, especially at the higher end.

If you add in SR, a caster-enemy with SR will become far more dangerous (as both the physical and magical/psionic characters would have to roll exceptionally well to get through with the lower probabilities, while at the same time needing to roll exceptionally well to resist or avoid the effects cast by the monster)

If you change the Save DCs, Saving Throws, ACs, and Attack Bonuses of the monsters to allow for similar hit/miss probabilities, then those concerns are moot, but that would require a greater change in the rules.
Steve W.
wilcoxon
Minneapolis, MN
Post #: 76
At least for 4e, almost everything is designed so that 10+ succeeds so using 2d10 instead of 1d20 should not change the odds of success significantly. However, it will make the intentionally very hard encounters even more dangerous as the chance to hit becomes even less.

The Arcanis system uses 2d10 instead of 1d20 (and has lots of other benefits over D&D/PF such as being (mostly) classless and skills based).

Shadowrun uses actual dice pools of Xd6 (though they work very differently between version 1-3 and 4) but it would be pretty much impossible to use this mechanic in a D&D/PF game.

The simplest would be to use whatever multiple of dice you want for the curve you want. 2d10 ranges 2-20 with 11 average, 5d4 ranges 5-20 with 12.5 average, 4d6-4 ranges 0-20 with 10 average, etc. The more dice, the steeper the bell curve (and less likely for extremes). If you want a simple drop-in for a d20 game, I'd probably go with 2d10.
Troy S.
SkullThrone
Minneapolis, MN
Post #: 43
I was thinking that all target numbers in the game would have to take a -1 or -2 from their d20 value, to account for the typical requirement of results of 15 or higher on the d20 to mean a "good" result. The 2d10 change seems like of an impact to the core mechanics than say 3d6+2 or 4d6-4, as like you mention the more dice the steeper the bell curve and the more tendency to be average.

I really haven't worked any of the math out beyond the basics. Just thinking about the game last night, I needed a 13 to hit a lot, and I rolled so many 12's (ok three of them, among other lower numbers), and curving this with 2d10 would only make things worse...However apply the -2 to all target numbers, then the 13 becomes the 11 which is right at the height of the curve. Now, the 13 was needed only after I was gaining flanking, so on a normal attack I needed a 15.

So, it maybe better for game play to allow 2d12, with doubles being the "crit" as above. The average would rise to a 13, and the overall range increases...now even players with a +1 in a skill would achieve a DC 25 result (less than 1% or the time), and you may not have to adjust the targets at all for they system to "work".

I'm also thinking about the opponents, we have an AC 22 Tank in the party, the 2d12s give creatures about the same base chance of needing a nat-20 to hit, but each +1 that the creature gets on a roll begins to be more significant as it pushes up the curve. So a +1 attack creature would hit 7% of the time, a +2 hits 10% of the time, and +3 nearly gets to 15%.

I doubt, I'd be able to convince the DM anyway...I have always loved the d20, and rolling a Nat-20 happens enough that everyone does it nearly once a session, just most the time its initiative of a perception check on an empty room (Last night I did roll it in combat and on the confirm rolled another Nat-20...that is much rarer).

I think maybe the 2d12 would probably be the easiest change, that could be done with no other modifications, it might result in more success on things, but honestly I don't know it that would be a bad thing.
William C.
user 43358752
Eden Prairie, MN
Post #: 13
Another thought would be to use an XdY, choose Z method (3d10, choose 2). Like the 4d6, choose 3 for Ability Scores. Using that, you can essentially target a certain number to be the top of the bell curve more easily. The main issue could be that very low numbers become increasingly unlikely, much moreso than very high numbers.
Troy S.
SkullThrone
Minneapolis, MN
Post #: 46
That's an interesting thought, as you could use the discarded dice as some type of other measurement or story telling lead (most likely the higher this is the better the effect)...or even hit location (for combat), so if a 10 was head you might choose the other two numbers if they were say a 7 and 8, hoping that the 15 would give you a hit, so you could get a head shot...or you might force them to always keep the highest two die for the result...making a 10 on this alternate effect a 1 in 1000 chance, and a 9 would be less than 1 in 100...interesting

Also you allow things like re-rolling 1, 2 or even all three dice for different Feats or even have say elves roll 4d10 (still keep 2) when searching for a secret door...or in penalty situations players may only roll 2d10 and take what ever they roll, or simply have "keep 1" situations when things might be really bad.

That definitely has so neat possibilities, great idea!
Steve W.
wilcoxon
Minneapolis, MN
Post #: 77
Giving it some more thought, I think I'd use the following (at least as a first pass) for drop-in replacement for the d20 rolls: 2d10 for 4e and 2d12-1 for 3.5/PF.

4e targets 10+ as typical success so 2d10 should work fine but it will make the "super-tough boss fight" even tougher.

3.5/PF tend to expect higher typical rolls for success so the 2d12-1 would probably work better (and the odds of getting >20 are only around 4%) - only thing I'm unsure of here is if crit should be on 20+ or something higher. In regards to crits, 2d12-2 would work better as crit fail on 0-1 and crit on 20+ - however, it lowers the average to 12 (which then may require some TN/DC adjusting).
Troy S.
SkullThrone
Minneapolis, MN
Post #: 47
Appreciate the thoughts, your insights on this have been very interesting.

I may have to run a campaign to try this out...I'm leaning toward the 3d10 (keep 2) or 2d12 system, I probably would go straight 2d12 if I did, and make any adjustments on the DM side, so players would always just roll 2d12+mod.

I won't know what adjustments I'd make to the TN/DC until I compared it to the actual adventure that I'd be running vs players bonuses.
Paul O.
user 4986770
Minneapolis, MN
Post #: 28
Lots of systems use variations on the dice pool concept.

Off hand, the original West-End Star Wars was very dice-pooly. Traveller uses 2d6 for the same reasons you're talking about using 2d10 (but the range of possibilities is pretty narrow). FATE gets great results from 4d3 but the GM and players have to work pretty hard to get the system to work for them. The Cortex system gets some very interesting results using 2dX (variable die size)

My favorite is GURPS (3d6 for most die rolls) because I really like the bell curve that results and the range of possibilities is pretty close to d20 so I can pretty easily convert over d20 materials.

Going out on a limb a bit, I once played in a modern Star Wars game where we used 4d6-4. It played great but we didn't continue the experiment because some of us found it surprisingly difficult to continually add up 4 dicelaughing
Troy S.
SkullThrone
Minneapolis, MN
Post #: 48
I can't tell you how often the phrase "Math is hard" comes up with the group I play with, even when the math is d20+5 or 2d6+4....and sadly we're all primarily engineers...sometimes we have the its late/I'm tired excuse, but other times it's just a brain fart...luckily theirs normally someone else watching the role that does the math fast and accurate, but then that's when the jokes come in.

I know lots of systems have great dice pool mechanics, but what I'm mainly looking for here is an easily system that grants more than 20 possibilities and that the results have a non-linear curve to them, and keeping the math as easy as possible. Many of the suggestions are great so far, thanks for the input.
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