d20 Call of Cthulhu

d20 Call of Cthulhu follows the d20 Modern rules, with the exceptions noted below.

Skills

Broadly speaking, skills work the same in d20 Call of Cthulhu as they do in d20 Modern. However, some specific skills work differently, as described below.

Animal Empathy: This works like the Diplomacy skill, only for animals.
Appraise: There is no equivalent skill in d20 Modern; this skill functions similarly to the Appraise skill in D&D 3.5.
Bluff: This skill functions similarly to the equivalent d20 Modern skill, with the exception that it cannot be used to send secret messages (see Innuendo below).
Cthulhu Mythos: There is no equivalent skill in d20 Modern. This skill functions similarly to the Knowledge skills, with three notable exceptions: it can never be taken as a core (class) skill, it can only be improved by reading Tomes or through direct Mythos experience, and it determines the characters Maximum Sanity (see below).
Disable Device: This skill functions similarly to the equivalent d20 Modern skill, with the exception that it cannot be used to pick a lock (see Open Lock below).
Heal: This skill functions similarly to the Heal and Treat Injury skills in d20 Modern.
Innuendo: This skill enables a character to send secret messages, similar to the Bluff skill in d20 Modern.
Open Lock: This skill enables a character to pick a lock, similar to the Disable Device skill in d20 Modern.
Operate Heavy Machinery: This skill functions like Drive or Pilot in d20 Modern, only for heavy machinery, such as forklifts, cranes, etc.
Performance: This skill is identical to the Perform skill in d20 Modern.
Psychic Feats: There is no equivalent skill in d20 Modern. This skill enables a character to perform psychic feats.
Psychoanalysis: There is no equivalent skill in d20 Modern. This skill functions like Heal, only for Sanity points (see Sanity below).
Read Lips: There is no equivalent skill in d20 Modern. This skill allows a character to understand what another character is saying by reading his/her lips.
Speak Other Language: This skill is similar to both Speak Language and Read/Write Language in d20 Modern. Characters must choose a specific language, and may have multiple ranks in a single language. Attempting to speak/read/write the language generally involves a skill check, and (depending on the circumstances) may be retried.
Spellcraft: There is no equivalent skill in d20 Modern. This skill enables the character to identify a spell being cast or already in effect, or decipher a spell from a tome without learning it first.
Use Rope: There is no equivalent skill in d20 Modern. This skill enables the character to tie and untie knots. Binding a character is an opposed check versus the prisoner’s Escape Artist skill.
Wilderness Lore: This skill is identical to the Survival skill in d20 Modern.

There is no Decipher Script skill.
There is no Gamble skill.
There is no Investigate skill.
There is no Navigate skill.
There is no Profession skill.
There is no Read/Write Languages skill.
There is no Survival skill.
There is no Treat Injury skill.

Sanity

Sanity is a new statistic in d20 Call of Cthulhu. It is a measure of mental balance. Strong personal experiences (such as exposure to horrific Mythos realities) leave emotional scars that weaken sanity. In game terms, this loss of sanity is represented by a reduction of Sanity points.

Starting Sanity: 5 times the character’s Wisdom ability score.
Maximum Sanity: 99 minus the character’s Cthulhu Mythos modifier.
Current Sanity: Initially equal to starting Sanity, this value will fluctuate during the adventure.

Sanity costs are given by two numbers or dice rolls, separated by a slash, such as “2/1d6.” Whenever the character encounters some horrific or gruesome scene, he/she must make a Sanity check. This is a d100 roll, where the DC is the character’s current Sanity. If the check succeeds, the character loses a number of Sanity points indicated by the first number (in the earlier example, this would be 2 points). If the check fails, the character loses Sanity equal to the second (1d6, in the above example).

Recovering Sanity: Characters may recover Sanity when they increase a level (+1d6 points), or as a reward for accomplishing some major task or quest (varies). A character’s current Sanity may never exceed his/her maximum Sanity, however.

Additionally, characters who undergo private care or institutionalization may recover Sanity points for successful Psychoanalysis, as described in Chapter 4 of the core rulebook.

Going insane: If the character loses Sanity points equal to half his/her Wisdom ability score from a single roll, he/she must make a Sanity check. Failure means the character goes temporarily insane. The effects of this condition are described by Tables 4-1, 4-2, and 4-3 in the core rulebook.

If the character loses 20% of his/her Sanity points in 1 hour, he/she goes indefinitely insane. This condition lasts 1d6 months, and is described by Table 4-4 in the core rulebook.

If the character’s current Sanity drops to 0, the character begins losing 1 point of Sanity each round, unless stabilized using the Psychoanalysis skill. When the character’s Sanity reaches -10, he/she becomes hopelessly, incurably, permanently insane. The character becomes an NPC.

Combat

Combat in d20 Call of Cthulhu is very similar to d20 Modern. Notable exceptions include:
Attacks of Opportunity: There are no attacks of opportunity
Actions: The only action types are Reaction, Free Action, Attack Action, Move Action, and Full-Round Action. There are no swift actions
Subdual Damage: Subdual (nonlethal) damage works like normal damage, except that when the cumulative subdual damage equals the target’s hit points, the target is staggered, and when it exceeds the target’s hit points, the target falls unconscious. Subdual damage heals at a rate of one point per hour per character level.
Firearms: Specific firearm rules include:

  • When using a weapon that has autofire, a character may use a full attack action to attempt two extra attacks per round, using the highest base attack bonus – 6 (each attack uses 3 bullets). Alternatively, a character may use a full attack action to perform an autofire spray. The character makes an autofire attack as described above, then continues firing as long as there is ammunition in the weapon; each additional attack uses 3 bullets and only hits on a natural 20 (this is not considered a critical threat).
  • When using a weapon that has multifire, a character may use a full attack action to attempt one extra attack per round, using the highest base attack bonus – 4 (each attack uses 1 bullet).
  • When using a standard weapon, a character may use a full attack action to attempt one extra attack per round, using the highest base attack bonus – 6 (each attack uses 1 bullet).
  • An unmodified attack roll of a 1 is an automatic failure. Roll 1d20 and compare it to the weapon malfunction table on page 81 of the core rulebook.
  • An accidentally dropped firearm with a live round in the chamber discharges in a random direction. Roll 1d8 to determine direction. If there is a target within 30 feet, roll 1d20-4; if this result exceeds the target’s AC, the target is hit.

Spells

Magic spells work differently in d20 Call of Cthulhu.

Learning spells: Spells are most commonly learned by studying Mythos tomes, although sometimes one can learn a spell by studying under a master, creature, god, etc.
There are no “spell levels.” Any character can learn any spell, so long as the character has access to the appropriate tome or teacher.

Casting spells: There are no “prepared spells” or “spell slots.” A character can cast any number of spells per day. However, most spells cost the caster sanity and/or ability score damage. Other people who know the spell can help a character cast it; doing so dividesthe ability score damage among them (rounding up), but each caster suffers the full sanity cost.
Spell failure only occurs if the caster’s concentration is broken, or the spell characteristics cannot be made to conform (e.g. wrong target type).

d20 Call of Cthulhu

Arkham, the Legend-Haunted City Stephen