Niche D20Base Casting Bonus
Base Casting Bonus (BCB) is a representation of your prowess as a caster. Similar to base attack bonus, not all base casting bonuses are equal between classes. As a result this doesn’t inherently mean a lower BCB character will be bad a casting, but they may lack access to some of the more complex castings on their high casting counterparts; this is usually balanced by lower BCB having higher BAB and high BCB having low BAB allowing for the mixture of magic and martial to be a higher or lower focus of the character.
Undercasting
You may cast a spell intentionally at a diminished effect at less than your maximum Base Casing Bonus, Casting Ability Modifier, or even Spell Prowess Bonus. You cannot reduce your Base Casting Bonus or Spell Prowess Bonus below 1 when undercasting. These decisions are made before the spell is cast.
Penalties to Base Casting Bonus
If an effect would reduce a caster’s BCB below 1 a creature becomes unable to cast; if this would occur as part of casting instead the spell is interrupted and is lost.
Casting Ability Modifier
Casting ability modifier (CAM) is usually determined by your class, either given depending on the class or a choice made within the class. Casters generally use Intelligence, Focus, or Psyche. Casting ability modifier is used to determine the spell’s save attack roll and number of spell points per day you possess. Some spells and other effects may have more uses for Casting Ability Modifiers.
Casting Ability Modifier From Multiple Sources
If a character has a casting ability modify from different sources (such as through multiclassing) they use the casting ability modifier of the class you possess the most levels in (if equal use the one you put levels in first), if multiple classes use the same modifier add the levels together for the purposes of determining the class with the most levels for the purposes of determining casting ability modifier. Casting ability modifiers themselves do not stack with themselves or each other.
Classes that allow a choice of casting ability modifier use the modifier chosen when the class was gained and do not allow for a change of this decision.
When gaining levels in a class that allows for the choice of casting ability modifier, the creature must choose the casting ability modifier that matches their current casting ability modifier if one of the available options would match, otherwise they may choose from the available options as normal.
Spell Prowess Bonus
Spell Prowess Bonus (SPB) is a representation of one level in casting classes. Similar to Martial Prowess Bonus (MPB) this helps determine a portion of the scaling on spells and abilities between classes. This is usually used to determine what the foe must roll against for saves; meaning as long as one continues taking levels in casting classes their spells may remain the appropriate power for the level they’re at.
Spell Save Attack Rolls
Usually when casting a spell with a save attached one makes a “Save Attack Roll” this is usually 1d20 + ½ SPB + CAM. The foe then rolls their appropriate saving throw against this resulting value. If a spell targets multiple creatures or lingers for multiple turns, roll the save attack roll once when the spell is cast and each creature rolls their saving throw against this value; each additional round the spell lingers a new save attack should be rolled if the spell calls for or allows additional saving throws against its effect, unless specified otherwise.
Save attacks behave as normal for automatic successes and failures as normal attacks. Spells normally cannot get a critical success effect for a natural 20, and instead simply determines automatic success and failure of the spell.
Creatures may always choose to willingly fail a saving throw treating themselves as having rolled a 1 on their saving throw.
Creatures making a save attack always know if their save attacks are successful, unless specified otherwise by the spell or the target has an ability that allows it to deceive the attacker.
Opposed Checks
Some spells or effects might call for a SPB check against a spell or effect. This is usually done by rolling the 1d20+ the SPB + CAM of both casters and comparing results to determine outcome; though this may differ depending on the spell.
Spell Pool & Spell Points
A spell pool is a resource pool that casters use to create various spell effects each day. A spell pool contains a number of points determined by the character’s levels in casting classes + their Casting ability modifier. Hybrid classes do not count as casting classes for the purposes of determining capacity of their spell pool despite usually granting a SPB value. Unless otherwise specified, a spell pool replenishes each day after a long rest.
Temporary adjustments to an ability score, such as through bonuses or penalties, do not affect a creature’s current or maximum spell points. Permanent adjustments to an ability score may increase the maximum but do not grant bonus spell points until the creature properly rests to regain the spell points. Permanent adjustments that reduce the maximum only reduce a creature’s current spell points if the maximum would become lower than the creature’s current spell points, reducing the current to the maximum value currently for the spell pool.
Not all spells have a spell point cost associated with them and thus usually can be cast without a limit per day. For spells with a cost, the cost should be deducted from your spell pool usually either at the time the spell was prepared or was cast (see the casting type section for more details). Some spells or modifiers to spells may incur additional spell point costs for the effect; the casting must be able to pay the entire spell point cost to cast this spell.
Spell Resistance
Spell Resistance is a creature’s ability to avoid being affected by spells. Some items, spells, and abilities may grant spell resistance, while some creatures have a natural resistance to magic in the form of spell resistance.
Spell resistance is represented as SR 5%, SR 10%; the number representing the creature’s level of spell resistance. Spell resistance similar to the miss chance of concealment requires the attacking creature to roll a d100 (or percentile dice), to determine success. If the value is equal to or lower than the creature’s SR value then the spell immediately fails to affect the creature.
Spell resistance is rolled before a creature would need to make an opposed saving throw against a spell, but after any required attack rolls have occurred to determine if the spell would hit or not. This is because if a spell misses a creature it would not be subject to the spell, while a saving throw is a representation of a creature’s ability to shrug off a spell that has already begun to affect them.
In the case of targeted spells this will prevent the spell or any effect related to the spell from occurring. Area of effect spells treat it as if the creature succeeded against any save related to the spell, and negates any initial damage or conditions caused by the spell; but lingering effects such as difficult or hazardous terrain may still affect the creature as normal for damage and saving throws.
Every spell details if it is affected by spell resistance or not as Spell Resistance generally only affects initial detriments, or conjured effects, but some spells simply launch objects, conjure hazards, or perform other mundane effects that don’t allow spell resistance to react against it.
Spell resistance is not an effect a creature normally willingly has available and instead is considered always on; meaning it may occur against both beneficial and detrimental effects regardless of the creature’s will at the time. A creature may spend 3 AP to suppress their spell resistance up to a maximum number of rounds equal to their Psyche modifier (minimum 1), chosen at the time the spell resistance is suppressed.