Shadowrun D8
by David Buehrer (graht@uswest.net)

Why Eight-Sided Dice?
Don't get me wrong, using six-sided dice to play Shadowrun works just fine. However, there's one little statistical hang-up that comes into play regarding Shadowrun's Rule of Six.

Because of the Rule of Six, the chances of succeeding whether the target number is a six or a seven are the same. The odds of rolling a 6 on a six-sided die is one in six. Using the Rule of Six, the odds of rolling a 7 is one in six, because the player must first roll a 6 and then roll a 1. The odds of rolling a 1 or better on a six-sided die is 100%.

The Twist
When using eight-sided die for Shadowrun, treat any 8 as a 0. I.E., treat the die as if it is numbered 0-7, substituting 0s for 8s.

By using an eight-sided die that is numbered 0-7 and changing the Rule of Six to the Rule of Seven, the aforementioned statistical hang-up is eliminated. If a character needs to roll an 8 to succeed, and one of his dice comes up a 7, his follow up roll might be a 0. Now every negative modifier (increase to the target number) counts.

What's the Downside?
Aside from spending money to buy more dice, I haven't found one. And I've thoroughly playtested this with my group. The odds of success for any given target number generated by using eight-sided dice numbered 0-7 are almost the same as the odds of success generated by using six-sided dice numbered 1-6. For some target numbers the odds are a little bit better, for some, a little bit worse. But generally the play of the game changes very little (except for those players who have been taking advantage of the quirk of the Rule of Six).

Using eight-sided dice numbered 0-7 for initiative creates a little more variance. But since everyone is using the same dice, the quick are still quick, and the slow are still.. well.. slow.

Making Dice Rolls
As with the standard Shadowrun rules, the gamemaster will provide the player with a target number against which he will make a dice roll. The player rolls the indicated number of dice and then compares each die result individually to the target number. Each individual die that scores equal to or greater than the target number is considered a success. The more dice that score successes, the better the result.

Target Numbers
The gamemaster determines the target number necessary for success in a test normally. See p. 92 of the Skills section for a list of target numbers based on the difficulty of the activity. No target number can be less than 1. If modifiers reduce the target number below 1, consider the target number a 1 for purposes of making tests.

Modifiers
Apply modifiers to the Target Number per the rules.

Rule of Zero
Any time a die roll result comes up a 0 in a test, that die is an automatic failure, no matter what the target number. But the test can still succeed as long as the other dice succeed.

If all the dice rolled for a test come up 0s, it means that the character has made a disastrous mistake.

Use the Rule of Zero when the rules refer to Shadowrun's Rule of One.

Rule of Seven
The Rule of Seven allows tests to succeed against target numbers greater than 7. When making a test against a target number greater than 7, the player may re-roll any dice that comes up a 7 and then add the new result to the 7. The player can reroll additional 7s if the current die result total is still less than the target number.

The Rule of Seven does not apply to initiative tests.

Optional House Rules

Target Numbers
No target number can be greater than 21. If modifiers increase the target number above 21, consider the task to be impossible.

Rule of Seven
Do apply the Rule of Seven to one initiative die. If a player is rolling only one die for initiative, than the Rule of Seven is applied to that die. If a player is rolling multiple dice for initiative, then apply the Rule of Seven to one odd colored die.