Recently, I have found myself gravitating towards games that include a task resolution mechanic that includes a way to measure the margin of success on a check. It started over a year ago, with my short-lived Witchcraft campaign, and then flowed into my year-long Corporation game , and recently it became a requirement for picking the system  for my latest campaign, In Nomine. Of all the mechanical elements  of a game, this is by far, becoming one of my favorites. The best part is, that even if your game did not come with one, you can add one pretty easily.
Nuts and Bolts
Lets take a moment to look at the margin mechanic in a little detail. In many games a task check (skill, combat, etc) has a Boolean result of either Pass or Fail. Mechanics that utilize margins change that Boolean result into a spectrum of Pass and Fail. There are a few ways that the margin mechanic can be employed:
- Success Only: In this case you can fail the task, but if you are successful there are levels of success, staring from marginal success and moving upwards.
- Bi-Directional: In this case there are both levels of failure and levels of success. Typically at the bottom there is a massive failure that improves to minor failure that becomes a minor success leading up to massive success.
In addition the margin can be:
- Fixed: there are a finite number of degrees of success and/or failure. Results that exceed the max result are counted as the max result only.
- Open ended: there is no limit to degree of success other than the margin of the check itself.
There are a few ways to determine the margin depending on the mechanics of the game system. Here are some of the most common:
- Difference in Target Number: In this case, there is a target number the player is attempting to roll over for success, after the roll, the target number is subtracted from the roll, and the larger the difference, the greater the success or failure. Some games only measure the MoS while others measure both success and failure. (example: Corporation, Witchcraft, Savage Worlds)
- Additional Successes: These are common in games with dice pools. There will be a set number of successes required for a task, and any additional success rolled indicate a greater success. (example: Burning Wheel)
- Check Digit Die: A few games will use a separate die that is rolled with the dice used for the check, or will designate one die that is being rolled for the check as the check digit. The result of this die, then determines the margin. (example: In Nomine)
- Task Matrix Table: Some games use tables for determining success; the better you roll, the higher the level of success is measured on the table. (example: Marvel Super Heroes)
As you can see the Margin mechanic is pretty flexible, but its real power comes when you pair the mechanic up with the GM…
Margins Are the GM’s Friend
It has been said countless times that the GM’s job is hard. It takes a lot to describe the action that is unfolding around your players, translating it into exciting prose that keeps your players interested and engaged. In the chaos of keeping all those elements together, we tend to take mental and verbal shortcuts in our narration. One of the most likely targets of these shortcuts are the descriptions of the outcomes of skill checks. Nothing is more painfully boring than saying something like, ” You jump across the chasm and land on the other side. Which direction do you go?”
You would like to vary your descriptions of such actions, but it is an easily forgotten task. That is where the margin comes into play. Because the Margin is baked into the mechanics, the GM has an instant reference of how well a player has accomplished a task. Now, that jump across the chasm has a few different possibilities:
- Marginal Success: “You land on the other side of the chasm, but fall onto the ground, your sword just out of reach.”
- Spectacular Success: “You land on the other side of the chasm, knees slightly bent, perfectly balanced, and ready for action.”
- Marginal Failure: “You jump and just fall short of the other side. You reach out wildly and grab the far edge, your sword tumbles into the dark abyss.”
- Massive Failure: “You jump. For a moment it looks as if you will reach the other side, and then you realize that you have grossly miscalculated the distance. You tumble into the dark abyss.”
In addition to aiding narration, there are a number of mechanical uses for the margin that can be used to help determine the outcomes of actions in a game.
One use is head-to-head contests. In this case, two adversaries are engaged in an opposed challenge. Both make skill checks and record their margins. The margins are then compared and the winner is the one with the highest margin.
The margin of success can be used to give bonuses or penalties to other checks. A skill check that succeeded with a high enough margin, would create a bonus for a subsequent check.
For instance: A stealth check, to sneak up behind a guard, with a high margin of success, would create a bonus to strike the guard on the next turn.
Another mechanic is to use a margin as a way to measure extended checks. In this case several skill checks are required for a task, but rather than requiring a set number of successful checks, you instead require a fixed number of margin as the threshold for completing the task. This use, rewards checks that have succeeded by a high margin, because they will reach the total required in less skill checks.
For instance: A character is researching an ancient tome for a ritual. The GM decides that it will require a total margin of 20 to discover the ritual, and that each check requires 1 hour’s time. The player that rolls a high margin on one more rolls, will reach 20 faster than someone who is marginally successful each check.
Making Your Own Margin Mechanic
If your game has a margin mechanic in it, then you are already enjoying some of the benefits mentioned above, but what about games where there is not a margin mechanic? You are not shut out from this great mechanic. In many systems it is not hard to create a margin mechanic, as a house rule.
In any game that uses skill checks with target numbers (for instance: D&D 3.x and 4e) you can measure the difference between the roll and the target number.
For instance: Your Cleric is making a Diplomacy check in order to obtain a donation from a Baron, for his church. The DM sets the DC of the check at 15 (the Baron does not hand out money easily). The player rolls and gets a 30. With a 15 point margin, the DM decides that the Baron not only decides to donate, but makes a very generous donation.
In many cases, experienced DM’s may be doing such things already. If you are, that’s great, if you are not, consider it. In either case, you can extend the margin mechanic and use some of the mechanical aspects, discussed above, as well.
For instance: Your Rogue is locked in a room filling with poison gas. The gas does 1d6 damage per round. The DM decides that the trap has a DC of 20, and that it will require a total margin of 35 to disarm.
So Whats Your Margin?
The margin mechanic is a great tool for GM’s, giving them a narrative guide, as well as some fun mechanics for creating tension in their games. So are you playing a game that has a margin mechanic? Have you house ruled a margin mechanic into your game? In what ways are you using margins?