I posted a while ago about converting Brandon Sanderson's Mistborn to my Travellers Beyond game. One part of that, which might not be easy to understand, is the Action Outcome system. TB is meant to be a modular-style game, that is, you can mix and match and connect different parts of the system to properly describe what you want. This design idea came from the birth of TB, when I liked the games I was playing, I just wanted to use different rules with their settings. So the hooks and classes describe something about your character and what he/she/it can do. But, you also need to know the outcome, the change in the game world, that comes from each action/ability. Which is why TB has 5 pairs of Action Outcomes:
The first pair deals with measurements:
⦁ Increase - raises a stat. Like 'healing', which increases your current hit points up to your maximum. Or 'boosting', which increases both your current and maximum totals. It also covers 'creating' or adding a brand new stat you did not have before.
⦁ Reduce - lowers a stat. So 'damage' lowers your current total, 'limiting' reduces current and maximum, and 'destroying' completely eliminates an existing stat (though, Darth Vader did say "no disintegrations" ;).
The second pair deals with control:
⦁ Operate - encourages something to happen. This is not a mod, like a +2 to a roll, rather it bends the odds, like roll two dice and take the highest. This can be for an action, so an Operate/Talker encourages you to talk to or interact with someone/anyone, or it could be for a target, so your best friend could be a form of Operate in that since they like you it is easier for you to interact with them (which, if you were fighting would also give you a bonus because you know them so well). I've also recently thought this could be used to off-set penalties. So, say the base target number to defuse the bomb is 15, but you have a -10 to your roll because it's raining and you're using your pen-knife instead of the proper tools. But if you had the special ability of "so awesome I can defuse a bomb with my teeth" it might be an Operate/Worker(bomb disposal) that would off-set the penalties (some or all) but still keep the base target of 15. Or, a thermal scope on your gun that can see through smoke would off-set the penalties for shooting through smoke, but not the penalties/target number for range or armor.
⦁ Constrain - discourages something from happening. This is kind of backwards from Operate. Operate/Talker makes it easier to talk, but Constrain/Talker makes it harder to do anything else. So, all Fighter, Explorer, Investigator and Worker abilities would be at a penalty (roll two take lowest) while Talker would be a normal roll. Rage, for example, is a Constrain/Fighter - it makes everything other than fighting harder to do (you could also say it was an Operate/Fighter making fighting easier/better too). Like operate this can be a type of action or a target. Note: I do not like "save-or-die" effects, and this includes mind control because I think taking away control of a character from the player is just about a cardinal sin of RPGing. Thus, while constrain makes something harder, it does not dictate what has to happen. The character can ignore or deal with the changes. So a "mind control" ability that makes a Constrain/Fighter and Constrain/your friends - that is, harder to not fight and harder to do anything targeting someone other than your friends - does not force you to attack your buddies, but it makes you pretty much useless otherwise (roll 2 or 3 take worst). This is a fine line, having control yet being crippled is not very fun either, but I think it is better than totally taking away control.
Next pair deals with information:
⦁ Understand - presents information. This is where the GM tells you more and more, and goes from generalities to specifics. So your "Undead Lore" ability means the GM will give you a breakdown of roughly, between x and y, how strong a skeleton or zombie is. I have sub-groups for present, past and future in here - so present is perception, seeing what's around you right now, past is forensics, looking at a crime scene and seeing where people where and what they did, while future is seeing something before it happens. The sub-groups are just to make some abilities cost more than others. So seeing the future costs more than seeing the past because in general seeing the future is more useful. It also makes fun twists like having a bonus to see the future but a penalty to see the present because your mind is so lost in what-might-be that you can't focus easily on the here-and-now.
⦁ Deceive - hides something or presents false information. So lies, stealth, disguises and forgeries, hidden doors and traps, fog - anything that makes it harder to tell what's going on. I don't yet have some sub-categories I like.
Then we deal with structure/change/interaction (not sure how to describe it in one word):
⦁ Transform - changes something into something else. For example, casting a spell that changes a sword from Reducing health to Increasing health is a transformation. Turning a person into a frog, or something colored green into something colored blue is a transformation. What you are trying to change sets the cost or difficulty, and it is all or nothing; that is, if you can't meet the cost then nothing happens. You can combine Reduce and Transform to get a sort of partial transformation effect, or create a nested list of transforms from cheapest to most expensive. (the all or nothing is just to distinguish this from increase/reduce, I want to keep each AO a separate type of effect)
⦁ Avoid - prevents a change, which could be any other AO really. Dodging out of the way, re-winding time, negating or cancelling an ability are all avoids. Like transform this is all or nothing.
Finally we deal with connections (or perhaps influence):
⦁ Bond - uses one thing to influence another. So your strength influences the damage you do with your sword, your teammate's feint creates an opening for you to strike (the 'aid another'), the lich comes back from the dead (or undeth?) until it's phylactory is destroyed.
⦁ Separate - negates influence. Pretty much this cancels an existing bond and I haven't found anything bigger for it yet. This last pair has not really fleshed out very well for some reason.
So, in the Mistborn conversion, there were two lines at the beginning of each ability like so:
Iron ("Lurcher") [Bender]
The first line has the name of the ability (and the type of hook, in this case "Bender" is a type of the Extraordinary Abilities hook), and the second line has the Action Outcome and Target. In the case above, the AO was Reduce, but specifically it was a Physical reduction, and more specifically a reduction of distance. The target was "Other," that is, not the character, and specifically metals only. So this power reduces the distance between the character and a source of metal.
Let's take a hypothetical example, and say we have a power that creates a field around the character that shields from laser beams. There are several different ways to describe this. If we say the field bends light, then it would likely be an Avoid/Physical--Self/light only. If the field interrupts or reduces light, it might instead be a Reduce/Physical--Self/light only. What AO is chosen effects how the ability works. In the first case, the Avoid, it would completely negate the laser/light-based attack up to the strength of the ability, but anything stronger would not be effected. That is, say the Avoid field is strength 5 and it is attacked by a strength 10 laser - the character would be hit by a strength 10 attack because Avoid is all or nothing. On the other hand, the Reduce field would instead subtract its strength from the attack, so in the above example the character would be hit by a strength 5 laser (the base 10 minus the reduce 5). However, every ability has a cost that is paid when the ability is used. So the Avoid would pay its cost (in "battery power" or "magic points" depending on the hook it comes from) only when attacked; while the Reduce would pay a constant cost while it was running (I know that sounds like splitting hairs, but in the overall system it makes some sense). Abilities may also have more than one AO. Take the Reduce light-bending field I've used for my example: I could add to it the AO of Reduce/Mental(perception)--Self/visual only. So the field would not only bend away light-based attacks aimed at the character, it would also reduce the character's visual perception ability, because all the light-bending makes it hard to see out of the field. Since TB is point-based, this type of disadvantage would help pay for the advantage of bending light in the first place.
The Action Outcome system is one of the parts of TB I am rather proud of. I think it does a good job of describing what something does, how actions effect the world, which helps when deciding how powerful an ability is/what it should cost and what that ability is good for/meant to do. If you want to use an ability in a creative way, the AO pairs and fields give you a framework to see how far away your creative idea is from the baseline of what the power was designed for. So far it also seems to be fairly atomic, that is, its the smallest set of building blocks for defining how something works. But, most importantly, what do you think? Feel free to leave some feedback/comments below.