The Conception
This idea came to me while I was thinking about the GUMSHOE dice mechanic. In GUMSHOE, your (non-investigative) skills function as a pool of points that you may spend to add a bonus to a die roll. Once the point is spent, it remains spent until the next time you have a chance to recover your resources.
This is quite different from how skills tend to function in game systems. In most games, a skill is more-or-less constant. If the skill is a modifier to a die roll, you always add the full skill; if it's a dice pool system, you roll a die for every point in the skill. In games like GURPS, your skill acts as the target number for your skill check.
GUMSHOE does away with this, treating a skill instead as a resource. It allows something many other systems don't: a character can become exhausted after an extended period of exertion.
So there I was, thinking about GUMSHOE, and I wondered what else we could do with skills. That's when it came to me: where GUMSHOE allows a variable die roll bonus, we could use a skill as a variable dice pool.
In a standard dice pool system, you roll one die for each point in your skill (sometimes with another component equal to a stat, or something else). For this idea, the skill instead acts as the maximum number of dice you can roll. You don't have to roll them all.
Why wouldn't you just roll all your skill dice with every check? We could do as GUMSHOE does, and treat the skill as an expendable resource: once you roll a die, that die is spent until your next recovery. Instead, however, I had a different idea. What if there were some risk to rolling more dice?
The Rules
The Wager Engine is a press-your-luck style dice pool mechanic, using six-sided dice. The GM tells you how hard the task will be, and you decide how hard your character will try to accomplish it. The harder you try, the more dice you roll, up to a maximum number equal to your skill rating. Any die that results in a 5 or a 6 is a success. Most tasks require only one or two successes, though harder ones may require more.
On the other hand, any die that results in a 1 represents strain. Your character has pushed himself too hard and suffered some fatigue.
A character has four attributes. In order from most physical to most mental, they are Physique, Endurance, Reflexes, and Intellect. Physique is your raw muscle; Endurance is a mixture of resolve and stamina; Reflexes is a combination of physical coordination and mental reaction time; Intellect is your ability to think through a problem.
Each skill is linked to one of these four stats. When rolling a skill check, any die that rolls a 1 results in damage to the linked attribute. When damage brings an attribute to 0, the character is exhausted and unable to perform any tasks linked to that stat. A Physique of 0, for example, is a result of exhausted muscles, while an Endurance of 0 could be coughing and wheezing while trying to catch your breath.
Mitigating the Risk
As-is, this system would actually punish a character for having higher ranks in a skill. The solution is simple: once a skill reaches a certain level, the character could ignore one result of 1 per skill check. Effectively, at a certain point, the character gets one risk-free die per use of that skill; her training allows her to push herself harder than the uninitiated. However, if a pool rolls two or more 1s, the appropriate attribute still suffers damage for each 1 after the first.
At an even higher skill rank, the character could ignore a second result of 1, effectively soaking two damage on each skill check.
For clarity, I'll call the ability to ignore a 1 "Mastery". Mastery 2, similarly, means ignoring two 1s.
Fiddling with Numbers
This idea would require plenty of playtesting to determine appropriate values for stat and skill maximums. My instinct is to say that skills range from 1 to 10, and a stat is the sum of all skills linked to it. For example, say Adam is playing a character with Climbing 3, Jumping 4, Lifting 2, and Brawling 3, all linked to Physique. His Physique would be 3+4+2+3, or 12.
The right skills would vary from setting to setting. Some games may require more mental skills (Intellect) than physical (Physique), or have almost no Reflex skills. The beauty of this method of calculating an attribute is that the value remains appropriate no matter how many or few skills it requires. If your game focuses more on Intellect and Endurance skills and less on Physique, characters will have higher Intellect and Endurance and thus be able to attempt more tasks associated with those attributes before succumbing to exhaustion.
Additionally, we have to determine at what value a character achieves Mastery. Crunching some numbers tells me that, when you roll four dice, the odds of getting at least one 1 exceed 50%. It seems appropriate, therefore, that when a skill reaches rank 4, you gain Mastery for that skill.
We have two options for the second level of Mastery. The odds of rolling two 1s doesn't exceed 50% until you roll 10 dice, so you could give the character Mastery 2 at skill rank 10. Alternately, we could go for the simplicity of doubling 4 to reach Mastery 2 at rank 8. Personally, I favor giving Mastery sooner rather than later, so I would give Mastery 1 at rank 4 and Mastery 2 at rank 8.
Using the Wager Engine
A friend pointed out that the system would work rather nicely for games in the horror genre. The fact that a character is slowly worn down over time, added to the fact that (almost) any action could result in increasing levels of fatigue, combines to build a sense of desperation and danger. It works significantly less well in games of high action, since a character is less likely to risk a large dice pool to achieve incredible successes when a smaller dice pool carries less risk.
We could build upon the mechanic in a few interesting ways. Rather than having a separate measure of "hit points", counting down the damage a character takes until unconsciousness or death, attacks could deal damage directly to one of the four stats. A nasty gash in the arm could damage your Physique, while a blow to the head could damage Intellect. This brings an added risk to combat: not only are you taking a chance that your character could die, but you're also losing valuable resources for accomplishing tasks later on.
Additionally, in games with magic systems, the stats could also be the resource you expend to cast your spells. Maybe a simple force arrow costs you a point of Intellect damage, and a fireball costs three Intellect. This is more organic than having a separate "mana points" number, since taking stat damage genuinely portrays the strain magic places on your body.
Alternately, you could determine the cost of a spell in dice rolled. That fireball spell might instead require you to roll five dice, taking Intellect damage for each 1 that turns up. Or it could be variable, with the damage linked directly to how many successes the spell roll nets, so that you need to weigh the risk on how many dice you're willing to chuck for that fireball. Spell Mastery could function similarly to skill Mastery.
Other things might be linked to this mechanic. Rather than keeping track of exactly how many gold coins your character is carrying, she might have a Wealth score and roll against it in the same way she rolls against skills. In this instance, 1s would measure large expenses that drain your coffers until your next windfall.
Give it a Try
Do you have any suggestions? Ways to improve upon the idea, or new ways to use it? Feel free to post them in the comments. Any feedback is welcome.
And if you try this idea out at your table, leave a comment telling me how it went!