Petersen Games – Rituals

Ritual magic makes use of science and mathematics beyond most mortal understanding to cast highly specialized spells. These techniques can be performed by anyone with the appropriate tools and knowledge without the use of formal spellcasting. Most rituals are held only in shunned books and in the minds of dangerous eccentrics who know more than is safe about the secrets of reality. Generally, these rituals depend upon knowledge of the alien sciences, extradimensional mathematics, and incomprehensible iconography of the cosmic forces underlying the Mythos.

Casting Rituals

Before performing a ritual, the primary caster must assemble and ready all the components needed as well as any secondary casters. The primary caster leads a ritual’s casting. Secondary casters can be indispensable to the ritual’s casting even when they’re not taking an active role in ensuring its success. To cast a ritual, the primary caster must learn the ritual’s secrets (Learning Rituals), though secondary casters can assist in the casting without fully understanding the intricacies of the ritual.

Casting Time: Casting a ritual usually requires 10 minutes per ritual level, but the casting time may be longer or shorter as indicated in its description. One of the casters—either the primary caster or a secondary caster the primary caster specifies—attempts one of the required skill checks at the end of each phase of the ritual. These checks cannot benefit from the aid another action, and the caster attempting the check can’t take 10 or take 20, even if she has an ability that would normally allow her to do so when threatened or distracted. Furthermore, because of the specific procedures of ritual casting, mundane equipment that grants bonuses on skill checks can’t usually increase the caster’s bonus on the checks required by the ritual, unless the GM allows it. Bonuses on the skill checks required for the ritual that are granted by feats, spells (with enough duration to last throughout the casting), traits, and magic items usually apply, at the GM’s discretion.

Components: Rituals can have any of the same components used by spells. Required focus and material components commonly include specific, unusual items. Feats and magic items that remove required components from spells do not affect rituals unless they explicitly say they affect rituals (or the GM rules otherwise). Rituals frequently require material sacrifices of blood or other vital substances.

Edible components must often be consumed during the ritual. Tomes are important focus components to many rituals, but whether they are mandatory or simply helpful varies from ritual to ritual. Optional components are listed after mandatory components.

In addition, some rituals have a locational component (“L”) or a temporal component (“T”).

Each includes a description for its component, which might be very specific (such as one particular hill) or general (such as “open to the sky” or “an underground chamber”). Temporal components are often astrological and require one or more stars or planets to be visible.

If these temporal or locational components are not provided, the ritual simply fails.

If a ritual allows the participation of secondary casters (often called “acolytes”), the ritual’s components line includes “SC” (“secondary casters”) as an entry, immediately followed by a parenthetical that details any maximum or minimum number of secondary casters required to cast the ritual. If a ritual description has no secondary caster entry, that ritual does not permit the assistance of secondary casters. While secondary casters can help by attempting the skill checks the primary caster assigns them, their chief purpose is to aid in the ritual’s casting. Unless stated otherwise in the ritual description, secondary casters must be within 100 feet and line of effect of the primary caster and each other during the entirety of a ritual’s casting.

A ritual automatically fails when enough of the casters are incapacitated, killed, or moved more than 100 feet from (or out of line of effect of) all other casters to reduce the number below the minimum number of casters.

Skill Checks: Since it is possible for those lacking the ability to cast arcane, divine, or psychic spells to cast rituals, variables that would normally rely on caster level (such as range and spell resistance) use the character level or total Hit Dice of the primary caster instead. This is the case even for a ritual caster who has the ability to cast spells. Characters with a caster level gain a +1 bonus on skill checks to cast a ritual, and this bonus increases by 1 for every 5 caster levels they possess (to a maximum of +5 at caster level 20th) as their understanding of the fundamentals of magic grows.

It’s surprisingly difficult to disrupt a ritual.

Participation in casting a ritual does not provoke attacks of opportunity, and the casters can pause the ritual to engage in combat or take other actions— though not without consequences. For each round a ritual is paused in this way, the DCs of all the ritual’s subsequent skill checks increase by 1. The ritual’s casting time does not continue to elapse while paused.

If all the skill checks for a ritual are successful, the ritual succeeds, and the primary caster (and the secondary casters, if specified) experiences the ritual’s backlash before the ritual’s effect occurs. If the casters fail any of the skill checks required for a ritual, or the ritual fails for another reason, the ritual ends. In this case, the casters also experience the ritual’s backlash, and the failure consequences occur (though only some rituals have these properties). The consequences of failure, if any, are detailed in each ritual’s description.

The skill checks must be attempted in the order listed, generally starting with the diagram skill check (if any), but the GM rolls for the checks and tracks the progress of the ritual casting in secret.

Mythos Taint: Any caster who has been tainted by cosmic forces gains a bonus on any skill check to cast a ritual, except for the diagram phase skill check. The bonus is proportional to the severity of the taint. The GM makes the final ruling on the severity of the taint, but as a general guideline, having a distant aberration ancestor or any fear condition caused by Mythos phenomena gives a +2 circumstance bonus. Belonging to a race linked to one of the Great Old Ones or other cosmic forces or having an insanity caused by Mythos phenomena gives a +4 circumstance bonus. Being a chosen vessel of a Great Old One or other cosmic forces or having multiple insanities caused by such creatures gives a +6 circumstance bonus.

Diagram Phase: The first phase of a ritual is usually the creation of an eldritch circle or other diagram. This phase’s skill check is labeled “(diagram)”. Having a tome or copy of the circle gives the caster a +5 insight bonus on this skill check. While not always in the shape of a circle per se, proper symbols, shapes, and glyphs are typically required.

Diagram: If a ritual calls for a diagram, it is described in this line. Diagrams generally must encircle the caster or the target as indicated in the ritual and cannot be moved once inscribed, even if the ritual’s casting is not yet complete.

Saving Throw: The DC for a saving throw against a ritual’s effects (if applicable) is equal to 10 + the ritual level + the primary caster’s Intelligence, Wisdom, or Charisma bonus (whichever is highest).

Spell Resistance: The primary caster makes any check for spell resistance using the effective caster level calculated from Hit Dice and any bonus from spellcasting class levels noted above.

Backlash: Any successful or failed ritual has a chance of draining the caster’s energy. The primary caster must succeed at a Fortitude saving throw or take 1 point of nonlethal damage per level of the ritual. The DC is 10 1-1/2 x the ritual’s level. All rituals have this backlash unless the description indicates a different one.

Failure: Any failure to cast a ritual has a dramatic psychic and physical toll on the casters, who become fatigued and shaken for a duration equal to the ritual’s casting time. If you use the Dread and Insanity rules, the save DC of the dread the participants gain instead of this shaken condition is 15 or 10 + 1.5 x ritual level, whichever is higher. In addition, the casters are frustrated by the principles and alignments necessary for that particular ritual.

They take a –5 cumulative penalty on skill checks to cast that ritual again for an amount of time equal to the casting time multiplied by the caster level. This penalty ends immediately for any caster later involved in successfully casting the ritual despite the penalty.

All rituals have this failure effect unless the description indicates a different one.

Learning Rituals

Learning a ritual from hidden clues or from independent research into alien sciences takes a week or a month per ritual level (GM’s discretion). Learning from detailed instructions takes an amount of study equal to 10 times the ritual’s casting time. In either case, the researcher must succeed at a skill check required by the ritual (learner’s choice of which). Failing the check means the secrets of the ritual elude the learner’s understanding, though she can start the process anew at the same rate of potential discovery.


Like spells, rituals are best-known for being hidden in particular Mythos tomes (described in Chapter 6), but can also be found in other texts. A few are associated with particular Outer Gods, Great Old Ones, or Mythos races, and are always carefully-guarded secrets.

GMs are encouraged to decide for their own games whether particular rituals are available, and where they can be found. They are often hidden away in places where seekers risk insanity or physical danger.

Occult Rituals

If your game uses occult ritual rules, these rituals can be adapted to function within that system with the following adjustments:

Casting Time: Increase the number of phases to equal the ritual’s level. The casting time generally changes to 10 minutes per ritual level, with a skill check every 10 minutes. If the casting time is already at least 2 hours, it is generally 1 hour per ritual level with a skill check every 1 hour instead.

Components: The ritual automatically fails if any of the casters are killed, incapacitated, separated by more than 100 feet, or are removed from line of effect to each other. If a ritual’s casting is aided by at least four secondary casters, all casters gain a +1 bonus on all skill checks attempted as part of casting the ritual.

This bonus increases by 1 for every four secondary casters beyond four (up to a maximum bonus of +5 for 20 or more secondary casters). This replaces any bonus listed in the ritual’s description for secondary casters.

Skill Checks: Increase the number of skill checks to equal the ritual’s level. The ritual doesn’t fail from failed skill checks until a number of failures equal to or greater than half the number of skill checks required occurs. The primary caster can choose any order in which to attempt the skill checks.

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