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Still struggling with 2d20 after a year

I’ve been gamemastering Mutant Chronicles for almost a year now, and I still keep confusing rules and forgetting others. Though I don’t play too often (less than 2 times a month) I already had the time to master any less crunchy system. It’s not that I dislike the system (I enjoy the Momentum/ Dark Symmetry pools and all that goes with it), but most mechanics have lots of variantes and exceptions, rather difficult to memorize. I even made a 20 page rules summary, but it doesn’t solve the problem.
I suppose my main problem is that my memory isn’t that good and I always chose simple systems in the past (this time I didn’t care about the system because I wanted to try Mutant Chronicles for a long time). Does anybody has been having this kind of trouble? And if so, did you find a some way to work around it?


I’m playing a non 2d20 game at about the same frequency. We also forget many of the rules.
If the ones you remember make a good game then don’t worry about it.

20 pages is too many ( school teacher mode activated) cut it down to the important stuff and ignore the exceptions you keep forgetting.

Players will remember exceptions that make them cooler anyway.


Oh, yes, the players remember everything they need to, alright. I’m not really worried, everything is going just fine while ignoring what I can’t remember. But if anyone has a trick they used in the past of some kind of “essential rules summary” (I’m not good at summarizing mechanics, numbers are not my thing) it would be nice to know about that.

Get yourself a one-page crib sheet for the rules you mix up or forget (even if its just a list of page references) - I run varying flavours of 2d20 and other RPGs and I often trip up over particular rules (like the burst rules in Call of Cthulhu - I’ve run that on and off for twenty years and still get tripped on that one). The crib sheet helps as a memory aid - but always remember tht if your players are having a good time, don’t nix it - DSP/Heat can always be used as a GM hand-wave to help cover mistakes.


I did not mention it before, but the fact that soon I will be gamemastering Infinity RPG and (probably) Conan too was the reason I started noticing the more confusing/ hard to memorize mechanics. The varying flavours you mentioned (in particular these two, Infinity and Conan) are very similar to each other and to Mutant Chronicles, but there are differences and nuances enough to turn occasional mistakes into a more recurring problem. I’m glad that, at least, I don’t have a rules layer among my players…

You think that’s bad? Try having a player that is already playing Infinity in one week, and MC3 in my game the other week. He is so damn confused, and it’s getting really hard to deal with.

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I ran Infinity, Conan, and Star Trek Adventures at UK Games Expo, and struggled to keep things 100% straight between the three… And I wrote the rules and have an extremely good memory for game mechanics. Hopping between slightly different games can vex anyone.


I’ve found it easier to deal with rules discrepancies when - and if - they occur, and admit to any mistakes. GMs have to juggle a lot more rules than players, especially if they run multiple systems :slight_smile: - and the Players Guides are extrmemely useful in that regard…

Tthank you for the feedback. Knowing that people who were directly envolved in the games sometimes face some of my problems makes me feel better! I suppose the main problem here is that for the last 30 years I’ve been avoiding (by mere chance, not by conscient choice) games with complex mechanics. Now that I’m getting older and less patient to memorize stuff I got stuck with a much crunchier system… Well, at least the settings are worth the trouble…


Have not visited the forums for a while, but yes, it is easy to mix-up the 2d20 games, unless you run them often enough or have a list, I call mine the 2d20 Gotchas. The first and most obvious one is the combat dice.

(1.a) Mutant Chronicles and Infinity both use the first iteration Combat Dice (CD) mechanic v1.1 that had D6 only dealing damage on a roll of 1 or 2 deals 1 or 2 points of damage respectively, with the 6 just being an effect without damage, thus, poorly crafted weapons without effects are inefficient. Mutant Chronicles actually refers to these as Dark Symmetry dice, but they basically function in the role of Combat Dice, so call them Combat Dice.

(1.b) Conan uses the next iteration of 2d20, that is v1.2, where the Combat Dice (CD) mechanic changes to allow a roll of 1 or 2 dealing normal damage, while the effects range is increased to include both a roll of 5 and 6 and furthermore, that 5 and 6 each deal 1 more point of damage respectively.

(1.c) Star Trek changes this even further referring to the Combat Dice as Challenge Dice instead (still CD though), the damage dice range is just like that of Conan. Thematically, Star Trek is not a combat focused genre but more of challenges and diplomacy.

(1.d) John Carter of Mars continues the Conan and Star Trek trend of Combat Dice and reverts back to the name “Combat Dice” so v1.2, but mechanically functions just like Star Trek and Conan.

(2.a) Then you have the powerful Hero Points, which are called Chronicle Points in Mutant Chronicles and each Player starts out with 3. The negative GM version is called Dark Symmetry Points.

(2.b) The Infinity RPG uses a similar mechanic but calls these Infinity Points vs the GM’s Heat Points or just Heat.

(2.c) Conan adopts the flavor of Robert E. Howard’s fiction (Crom sends you dooms), and calls these Fortune points vs Doom for the GM.

(2.d) Star Trek Adventures restricts the prevalence of these powerful Player Hero Points and calls them Determination and locks them into a narrative character tool called Values, so you which control the triggering of this Determination point. Players start out with just 1 Determination. The GM version is called Threat.

(2.e) John Carter of Mars Hero Points are called Luck and the negative for the GM are Threat. The heroes get lots of Luck points since they are linked to the weakest attribute which is 4 for everyone unless they boost it during character creation.

(3.a) This too changes with the most complex being in Mutant Chronicles, with physical injuries starting out being tracked against each major body part (head, torso, arms, legs), then shift to a single track of Serious Wounds, and finally to one for Critical Wounds. Mental injuries are tracked differently with Mental Wounds and then Dread tracks.

(3.b) Unlike Combat Dice, the Infinity RPG chose a slightly simple physical damage track, with no longer tracking each major body part but just two tracks of serious and critical, with Physical body damage called Vigor then more serious ones called Wounds, while the mental ones start with Resolve injuries and then Metatoia. There is another group specially for this RPG, called Firewall damage and its critical track called Breaches.

(3.c) Conan adapts the Infinity RPG injury track but without the hacking set, so just Vigor injusries and critical injuries called Wounds, while the mental ones being Resolve and critical ones are Trauma.

(3.d) Star Trek continues this simpler wounds system, but renames these to be Stress instead and unites the physical and mental ones into just a single Stress track. Probably, this is to streamline damage in Star Trek which is not a damage focused genre.

(3.e) John Carter of Mars changes this simple wounds by targeting the Attributes directly, so you have the Injury track (affects Cunning and Might injuries), Fear track (Daring and Passion injuries), and Confusion track (Empathy or Reason injuries).

(4.a) Mutant Chronicles has the most attributes (8) on the Character Sheet, with Agility, Awareness, Coordination, Intelligence, Mental, Personality, Physique, Strength

(4.b) The Infinity RPG has similar attributes (7) with slight modifications: Agility, Awareness, Brawn (combines Physique and Strength), Coordination Intelligence, Personality, Willpower (instead of Mental)

(4.c) Conan matches the exact ones from Infinity attributes (7) of Agility, Awareness, Brawn, Coordination, Intelligence, Personality, Willpower

(4.d) Star Trek takes a slightly different track on attributes aligned to to Starfleet’s three primary divisions, with 6 attributes which are: Control, Daring, Fitness, Insight, Presence, Reason. Star Trek also gets rid of the many skills in previous 2d20 games and just focuses on those Starfleet divisions of: Command Division (Command, Conn), Operations Division (Security, Engineering), Science Division (Science, Medicine).

(4.e) John Carter of Mars continues the trend for few attributes (6) and closer to Star Treks, but themed for the Barsoom novels’ themes of Daring, Might, Cunning, Passion, Empathy, Reason. Most importantly, John Carter of Mars throws out all the skills and just uses two attributes in combination in lieu of any skills.

Maybe another time, we could discuss the differences in Momentum spends across all these 2d20 systems. This long write up is just a quick overview of how similar yet how different all the 2d20 games can be rules-wise.


For me, 2d20 isn’t a system that I can grasp easily on paper. I need the gameplay experience to show me how the moving parts fit together. If it’s not intuitive for someone else, I suspect that might be part of the reason for them, too.

I’ll slip into “language teacher mode” for a second here, because I think this principle applies to gaming as well: memorization is a cramming technique, not a learning technique. Like vocabulary in a second language, immersion and usage are your best friends for learning rules. I’m all in favor of the cheat sheet, because I know my memory won’t hold all of that just because I want it to. I have a player who can keep track of rules in her head (bless her soul, because she’s not a rules lawyer about it), so that’s another resource if you are so lucky.

Can I suggest watching some twitch streams or you tube videos of people playing to gve you a better understanding

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I ran Infinity, Conan, and Star Trek Adventures at UK Games Expo, and struggled to keep things 100% straight between the three… And I wrote the rules and have an extremely good memory for game mechanics. Hopping between slightly different games can vex anyone.


Definitely. I have run various flavors of D&D so long I can’t always keep all the variations straight. I think the best thing to do is just run with it. Having a short cheat sheet (like a page or two) can really help, especially if you can delegate reading it to a player.

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I’m so glad it’s not just me.
I have JCoM and STA (and Infinity, but I haven’t yet cracked the books on that one) and they confuse the heck out of me. Thanks to everyone for the suggestions provided here. With the current “stay home and avoid Coronavirus” situation hitting the globe, it’s a good time to hunker down with the rule books and try to figure this out.

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I’m hoping the Modiphius streamlines 2D20 a bit more, and simplify types of damage and conditions.
Also i would like to see Mutant Chronicles 3.5 or 4 having these revised rules.

The new Dishonored 2d20 is supposed to be a more streamlines version


It’s been sounding like every latest iteration has been just a little more “streamlined.”


Though I have only browsed it, it is more streamlined, but has the same aproach to rules as Fallout 2d20: it tries to emulate the videogame. Adapting this streamlined rules to other settings might be a bit difficult.

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Several posters had suggested a cheat sheet. I don’t always know what to put on one of these. Are there any online cheat sheets that I can download to look at in order to help me figure out the various systems?

Absent a “basic” Momentum system, you might be interested in what I built here for Conan.

I was using the official GM screen for a few sessions before I realized it was almost useless to me as a GM. I’d recommend GMs try using it for a session or two. Then I’d say, “You got it down now? Difficulties go from 1-5 and so on? Great, now hand that screen over to the players.”

Then, if the GMs don’t make their own, I’d hand them this one:

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