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Alias
2013-01-03, 11:43 AM
Recently I've been toying with a new system with my group. We play Pathfinder and Savage Worlds (SW) heavily, and I've been running D&D Next playtests as well. So all of these are mulling around in my mind. And has been for the last year. I'm not in an especial hurry on this.

Recently I stumbled upon a core mechanic idea. It's not wholly new, it's a bit like inverted Alternity to be honest. And it takes a clear cue from Savage Worlds. The mechanic is

d20 + ability die (d4 to d12) + skill die (if applicable, also d4 to 12).

The reasoning is that while I'm a huge fan of Savage Worlds, the odds math is both wonky and narrow. You only have one target number. I want a system that allows me to eyeball things as a GM into "easy", "normal", or "hard". Adding a d20 into the mix widens the potential target number range, and adding the ability die widens it further from Savage Worlds, and it also creates a strong bell curve effects so that higher (and lower) target numbers become statistically more rare than the numbers would indicate from someone coming from a linear roll system like d20 (Savage Worlds, thanks to its ace rule, isn't linear. Schizophrenic may be the best word).

So, Easy - 15. Normal - 18. Hard - 21. The system works just fine if you never use any other targets, but if you're inclined to the math works out like this.

12 would be very easy. d20+d4 rolls 12.5 or higher 50% of the time, so DC 12 is a check result that is only going to be failed regularly by someone with minimal ability and no skill at all.

15 - d20+2d4 rolls 15 50% of the time or higher, so it's easy because minimal skill and ability are needed to accomplish this at least half the time.

18 - d20+2d6 rolls 17.5 50% of the time so a character with average ability and training will succeed slightly less than half the time. If the character is good (d8) at either his odds go up to 18.5.

21 - d20+2d10 hits hard half the time (avg roll 21.5). If we stop here we are fine. We can still go up though, in steps of 3.

24 - Very hard, bordering on impossible for the ill suited character. d20+2d12 rolls 23.5 half the time, and they are the best of the best so even they are failing slightly more than half the time. A character with minimal ability and no skill can hit this target number, but only has a 1 in 800 shot of doing so.

27 and 30 are the last two - both of which are flat out impossible for the weakest characters. The best of the best can do these things, but with a high possibility of failure. Target numbers past 30 can only be hit by characters with high ability and skill at all, and then are hit rarely. A 44 is the highest possible target number, with a 1 in 2880 shot of being hit by the rare characters that can hit it (That's significantly worse odds than being dealt a full house [507.8:1] and about half the odds of being dealt four of a kind [4164:1] )

A mechanic is the beating heart of any system. If it isn't fun or fair everything else falls apart. Also, if it isn't interesting there's not much elsewhere to go, so I'll stop here for now to see if there's any interest in discussing this further.