This post is one of a series of house rule posts for the Swords & Wizardry Core Rules. (S&W is a free 0e retroclone.) These posts are draft conversions of some of the house rules I've used in my campaigns for many years to Swords & Wizardry. Final versions of these rules will eventually be collected into a supplement for S&W that I can give my players. Comments are welcome. I realize that many people will hate one of more of my house rules for one reason or another. That's fine by me, but will not stop me from using them as in their original forms, most have worked well in my campaigns for many years.
[It'd be very easy to want a class for everything in S&W (Thief, Ritualist, Ranger/Scout, etc). However, that would soon get out of hand. Backgrounds make it easy to create "sub-classes" of the major classes as needed, with little effort.]
Characters may select, with the approval of the GM, a one or two-word background that represents a broad base of skills and knowledge, e.g. Thief, Prospector, Lawman, Engineer, Scout, Merchant, Ritualist, etc. Backgrounds need not be related to the PC's class -- they can be seen as something the character used to do or does on the side. For example, a Cleric might have been a thief before he felt the call of gods.
The GM should consider the character's background just as he would the character's class when deciding if a character would succeed as an action. For example, a character with an Engineer background should have a much better chance of damning a creek or building a bridge over it than a character with a Merchant background.
[This system takes into account Backgrounds as well as Class. It would only be used when the GM decides an action should be decided randomly instead of by GM decision.]
If the GM decides a random success chance is truly needed he will call for one of the following rolls:
Primary Attribute Roll:
Use: when a character is attempting something directly related to their class or background.
Roll: 1D20 + Attribute Modifier + (Class Level/2, round up)
Secondary Attribute Roll
Use: when a character is attempting only weakly related to their class or background.
Roll: 1D20 + Attribute Modifier + (Class Level/3, round up)
Minor Attribute Roll
Use: when a character is attempting something not related to their class or background.
Roll: 1d20 + Attribute Modifier + (Class Level/4, round down)
The Attribute Modifier is: (Attribute-10)/2, round toward 0.
When the GM calls for an attribute roll, he will declare the difficulty, type and attribute for roll, and any situational modifiers and the player will make a skill roll. Example: "Make an Easy Secondary DEX roll at -3 because it's pouring down rain." The player must roll higher than the target number set by the difficulty to succeed. Target numbers are Easy - 8, Normal - 12, Difficult - 16, Hard - 20, Very Hard -24, Legendary - 28, Unbelievable - 32.