CoC Rule Summaries and House Rules
Checks and Opposed Rolls
The following rolls may be called for by either the GM or Player:
- Idea Roll: represents hunches and the ability to interpret the obvious.
- Luck Roll: did the investigator bring along some particular piece of gear? Did they step on a floor board that squeaks?
- Know Roll: represents what’s stored as intellectual “trivia” or other miscellaneous known facts.
Ability rolls are d100 rolls against a particular ability score. Sanity Checks and Attacks are examples. Success is a roll equal to or less than the ability score.
Resistance rolls are d100 rolls that pit one characteristic against another. A player trying to open a stuck door is an example. Success is a roll equal to or less than the value from the Resistance Table, which can also be calculated as follows:
Example 1: a player with STR 14 vs. a door stuck with STR 12.
Example 2: a Monster with POW 16 casting a spell against a player with POW 10.
Opposed rolls are d100 rolls that pit one character’s skill against another’s. A Spot Hidden vs. Hide is an example. Opposed Rolls are resolved in the following manner:
- Opposed rolls only matter if both characters succeed, unless some other factor automatically provides a bonus.
- Character is attempting to hide behind a desk with a Hide of 50%. He rolls 67; a failure.
- A character attempting to spot the hiding character automatically succeeds.
- Opposed rolls matter if some other factor automatically provides a bonus.
- Character is attempting to hide in a dark cemetery behind a tall tombstone.
- The darkness and tombstone provides a +30% to Hide.
- The character has 50% Hide, for a total of 80%, but rolls 92% – a failure.
- An Opposed Spot Hidden is still needed, but success is based solely on the Spot Hidden characteristic.
- A character attempts to spot the hiding character in the darkness with a Spot Hidden of 40%. He rolls 39%, which is a success, so he spots the character.
- If both characters succeed, then the winner is the one with the highest degree of success.
- Character is attempting to hide behind a desk with a Hide of 50%. He rolls 32; a success that creates an 18% difficulty (50-32).
- A character is attempting to find the hiding character with a Spot Hidden of 70%. He rolls 65; a success that resolves to 5% (70-65).
- Even though he succeeded, he fails to spot the hiding character because his 5% does not meet the 18% difficulty.
- If both characters succeed and one has rolled a natural 1%, it is an automatic success over the opposed roll.
- Character attempts to hide in a dark cemetery behind a tall tombstone that adds +30% to Hide.
- Character has 50%, for a total of 80%. He rolls an 11; a success that creates a difficulty of 69%.
- A character is attempting to find the hiding character with a Spot Hidden of 40%. (The lowest possible roll provides only 39% success value (40-1), so there is typically no possibility for success.)
- The character rolls 01, which is an automatic success against the difficulty, so the character spots the hiding character.