One of the most interesting role playing game systems I've come across lately is Mutants & Masterminds 3rd Edition. This system is d20 based, but only loosely. They've done a great deal of creative thinking around how damage and powers work within the system, as well as how it scales. The scaling is truly the most interesting part to me. I've seen a lot of systems over the years that attempt to scale damage, and none of them really do a great job of it. Quite frankly, I don't see this as d20 at all - it's that different. That said, it only uses the d20, so it's almost more deserving of the name! But I digress.
Tree chopping vs. "Capn', she canna take much more o' this!!!"
It's easy enough to model two guys punching each other toward victory. The tree-chopping affect of 1d4 or 1d6 damage opposed to 20 or so hit points is not a lot to deal with. But scale such a system up to a starship with potentially tens of thousands of hit points, and ask yourself how that same system would work. First, a person's fist would do little against such a structure. Even a bullet or a modern rocket would likely do little more than scratch the paint. Such a vehicle has immunity to such lame weaponry. I've seen some systems try to account for this, but only using math and rules that are complicated, inconsistent and even limiting. They don't scale up or down. So you end up with wild swings in power.
If you've ever watched any episode of Star Trek, you know that it takes far less than the maximum number of hit points to be exhausted before Scotty (or Geordi) start losing their minds in engineering. The M&M system handles this with degrees of failure. A superior blast from a Borg ship may have the Enterprise on its knees after one shot. But again, the nice thing about this system is that it scales. So when the next biggest thing in the universe shows up with a planet busting weapon and fires it against the Borg cube, the cube is in relatively similar hot water. There's no flat "big damage vs small damage" line that's drawn as there is in systems like Savage Worlds. There's varying degrees of damage and failure that can happen at any level.Mutants & Masterminds approach is an exponential ranking system that can work surprisingly well at almost any scale. It does dilute the details a bit, but honestly, when we're talking about the difference between a claymore and a bastard sword... do we really need to nitpick? As long as a dagger is a little different from both of them, I'm happy to lose out on the detailed accounting for such things.
Why Mutants & Masterminds?
But M&M is pegged as a system for super heroes and super powers. Well, I like it so much that I think it could be easily adapted to suit any other genre as well, including horror, sci-fi or even fantasy. I believe M&M could be as flexible and adaptable as Savage Worlds -- which is another fantastic system, and one that I'm learning more about every day. But I think M&M could offer some benefits over it still. In particular, as mentioned above, I feel that M&M can scale far better than Savage Worlds.
If I want to run a scenario whereby Wonder Woman's invisible jet gets sucked through a wormhole in space and is transported into the middle of an epic starship battle, one that has been overrun with vampires, only to be intercepted by a wing of Gundam mecha and Baymax from Big Hero 6, who's trying to stop a planed busting weapon created by Thanos, then I want Mutants & Masterminds. I honestly don't think any other system can scale to handle it. And easily, using the exact same rules, with only a d20.Not that every scenario needs to be this ridiculous to warrant a M&M conversion. There's simply some great content out there in some of my other game systems, that I want to use in a M&M scenario.
Luckily, most other systems out there use very similar math.
Fibonacci to the rescue!
So how do we map flat, linear, tree-chopping hit points, attack damage and typical XdX dice rolls to an exponential ranking system?
As it turns out, mapping hit points and attack damage as a Fibonacci sequence manages to translate all hit points and attack damage from nearly any other system into M&M rankings quite easily. Fibonacci has the effect of bending the linear nature of typical RPG math toward the shape we want for Mutants & Masterminds rankings. At the very low levels, I simply map 1 to all the low values. This gives M&M a little finer granularity at the low levels, and more coarse granularity at the high levels. But honestly, I would imagine that few people play with low values as the rule. If M&M has a flaw, it's that it uses flat circumstance penalties and bonuses of -2 and -5, meaning that the system gets a bit weak at rankings of 5 or lower anyway. But for the majority of the cases, this will satisfy. And if it doesn't... just change it so that it makes sense for your situation.
As for character attribute levels, most games use the same 3d6 attribute rankings, with bonuses or perhaps extra attribute dice. They are almost always opposed to a D20, so their values generally represent about the same ratings. Large robots, creatures and super humans can be mapped in a similar way.
Limitations and Adjustments
So is there any system that this doesn't work for? Absolutely. I wouldn't try converting Savage Worlds using this approach. But I would never do so anyway. Savage Worlds is another system that I would target moving content to, not from. Luckily, Savage Worlds already has numerous Companion books for sci-fi, fantasy and horror that make conversion a breeze without any of my extras here. I would consider it for situations where I'm not worried about scaling or diversity in a single scenario - or for games with simply less super people or equipment.
In this table, I've accounted for very high numbers, as one of the more interesting themes to me is sci-fi, which demands large starships with massive amounts of hit points. Do I want to see Superman as presented in DC Adventures (an awesome M&M setting based on the comics) punch a starship, or a planet? Why yes I do...
Depending on the system you're coming from, you may want to shift the ranking up one row (thus Rank 0 would translate to 8 hit points or 1 attack damage). Or you may decide you want to offset the damage one row separately from the hit points. Moving things up or down a row will probably slot the system of your choice in line with the M&M rankings pretty easily.You may initially be disappointed when converting your characters, thinking they aren't powerful enough. Well keep in mind that M&M is a supers game. And most low level characters from fantasy or sci-fi settings are little more than normal people. This is especially true of sci-fi settings where they're still normal people even at high levels. But that's where equipment, devices and vehicles come in. The M&M Gadget Guides has all the rules needed for equipment, vehicles and even mecha from anime fame to power up your character. So if you want to see how Iron Man would fare against a Gundam armor, then knock yourself out!
I won't underestimate the effort to convert or create content that isn't available from the publishers themselves. But what I can say is that with a little practice and the examples in all of the M&M Gadget Guides, Power Profiles and especially the DCA Heroes and Villains books (Vol 1 & 2), you have more than enough examples to piece ideas together.
Hey wait, is this legal?
Absofrickinlutely. The table below is a list of numbers and dice rolls that are used in tens or even hundreds of role playing game systems. They're mathematical dice formulas and dice statistics, which cannot be protected by copyright. But I would warn against publishing conversions or creations of any content for which the IP is owned and protected by copyright. So if you do make Iron Man and Gundam suits... keep them to yourself or seek permission (which you aren't likely to get).
The thing is, converting and creating things will become very quick and easy. Nobody is doing anyone any favors by publishing their interpretation anyway. Yours may differ and suit your campaign better.
You're not striving for perfection, just close enough to get the point across so that you can focus the rest of your attention on the game. And by no means do I recommend trying to convert entire games over. That would be far too much effort. Covert what you need for your game and move on. You'll find that this way you won't be spending more time converting content you'll never use than playing the game!
In case I'm wrong on the Internet...
I haven't had the opportunity to test this out enough to call it perfect. It's highly unlikely that it is. So please feel free to leave a comment with improvements and suggestions.
Some of the numbers in the table aren't absolutely mathematically correct. I moved some things around based on gut feeling. If you disagree, point it out. It might just be a typo too.
Available as PDF and Excel.