RPG Design Patterns

Faction (Cthulhu vs. everyone else), Game Master, Generalized Contest, Hit Points, Last Man Standing, Random Attribute, Rank (Skill percentages), Resource (Magic Points, Sanity Points), Skill

Characters (“Investigators”) have 9 attributes whose values are generated randomly. These attributes are: “Strength” (STR), “Constitution” (CON), “Size” (SIZ), “Intelligence” (INT), “Power” (POW), “Dexterity” (DEX), “Appearance” (APP), “Education” (EDU), and “Sanity” (SAN). They also have three major resource pools from which to draw: Hit Points, Magic Points, and Sanity Points. These resources are determined by various formulae based on the attributes. Each character is assigned an “Occupation,” such as “Antiquarian,” “Dilettante,” or “Professor.” Each occupation is associated with a set of skills in which the player distributes a number of “Skill Points” whose quantity is determined by the character’s Education attribute. The resulting values essentially set the percentage chance that a character has in succeeding at each skill.

The “Cthulhu Mythos” skill is special. Gaining ranks this skill lowers the character’s Sanity Point maximum. So, the more a character learns about the true and terrifying nature of the universe, the less stable he becomes. Sanity Points may Points may vary anywhere from zero to the modified maximum. But if it ever drops to zero, the character goes completely insane. The mere sight of a Lovecraftian horror usually costs a character a portion of his sanity.

Each skill in Call of Cthulhu has a rank, which sets the percentage chance of the skill succeeding. To determine success, d100 is rolled. If the resulting value is less than or equal to the skill value, the skill succeeds, although a roll of 00 always fails. If the conflict involved weapons and combat, a successful roll indicates that damage is delivered to the target by rolling dice appropriate to the weapon used. If the target has armor, the damage is reduced by an amount depending on the armor’s type.

To resolve tasks involving attributes (“Characteristics”), players consult a table that pits one attribute against its opposing attribute. The table provides a percentage chance of the action succeeding.

Call of Cthulhu uses a karma-based initiative system in which character actions are ordered according to DEX, going from highest to lowest. In the case of a tie, the system becomes fortune-based with each player rolling d100 and going in order from lowest roll to highest.

The first time a character successfully uses a skill in a dangerous situation on an adventure, he gets to place a check mark next to the skill on his sheet. At the end of an adventure, the player then determines if any of the check marked skills improve. To do this, the player rolls d100. If the result is greater than the skill’s current rank, the player adds 1d10 to the rank of that skill. Thus, skills in which a character is a novice improve easily, but those in which he is expert rarely improve with use.

If the resulting percentage increase raises a skill above the 90% mark, the player gets to add 2d6 points to the character’s Sanity Points. Joy of joys! Your character gets to stay sane a little longer!