|d20 Modern System Reference Document|
Arcane spells, divine spells, and psionic powers are all representative of abilities beyond the scope of most ordinary individuals, and are called as a group FX abilities. FX abilities are features of a few advanced classes, and are not available to basic classes. FX abilities have a number of similarities to each other as well as obvious differences.
Distracting Spellcasters and Psionic Characters: A character can ready an attack against a character or creature with the trigger "if he or she starts casting a spell or manifesting a power." If the attack succeeds in damaging the character or otherwise distracting him or her, he or she may lose the FX ability he or she was trying to use (as determined by his or her Concentration check result).
Readying a Counterspell: A character may ready a counterspell against a spellcaster (often with the trigger "if he or she starts casting a spell"). In this case, when the spellcaster starts a spell, the character gets a chance to identify it with a Spellcraft check (DC 15 + spell level). If the character does, and if he or she can cast that same spell (are able to cast it and have it prepared), the character can cast the spell as a counterspell and automatically ruin the other spellcaster's spell. Counterspelling works even if one spell is divine and the other arcane.
A spell is a one-time magical effect. Magic is used by individuals with magical power, which include spellcasters and creatures with spells and spell-like abilities. Spells can be arcane or divine.
Arcane spells involve direct manipulation of mystic energies. These manipulations require long study, and tend to produce dramatic results.
Divine spells draw power from an unworldly source, be it from within the caster's own beliefs or some greater entity of power. Divine spellcasting requires meditation and provides more utilitarian effects, including the ability to heal the wounded. Some spells may be cast by both arcane and divine caster, functioning as arcane spells when cast by arcane casters and divine spells when cast by divine casters.
Most spells require the caster to speak some utterance, make complex gestures, or sometimes expend an object or a small quantity of some substance. The spellcaster's activity is visible to others, and the effects often are too, but the magic itself is not.
Each spellcasting advanced class learns and casts spells differently. See the class description for more details.
If a caster ever tries to cast a spell in conditions where the characteristics of the spell (range, area, and so forth) cannot be made to conform, the effort fails and the spell is wasted.
Spells also fail if the caster's concentration is broken. Arcane spells (but not divine spells) might fail if the character is wearing armor while casting a spell that has a somatic component.
Arcane spells involve the direct manipulation of mystic energies. These manipulations require natural talent and long study.
Compared to divine spells, arcane spells are more likely to produce dramatic results, such as flight, explosions, or transformations.
The rules for which spells, and how many spells, an arcane spellcaster can cast are given in the class description. The class description also includes information on how the character prepares spells each day.
To decipher an arcane magical writing, a character must make a successful Spellcraft check (DC 20 + the spell's level). If the check fails, the character cannot attempt to read that particular spell until the next day. A read magic spell automatically deciphers a magical writing without a skill check. If the person who created the magical writing is on hand to help the reader, success is also automatic.
Once a character deciphers a particular magical writing, he or she does not need to decipher it again. Deciphering a magical writing allows the reader to identify the spell and gives some idea of its effects (as explained in the spell description). If the magical writing was a scroll and the reader can cast arcane spells, he or she can attempt to use the scroll.
Unlike arcane spells, divine spells draw power from the strength of the spellcaster's beliefs. Divine spells tend to be less flashy, destructive, and disruptive than arcane spells. What they do that arcane spells don't do is heal.
The rules for which spells, and how many spells, a divine spellcaster can cast are given in the class description. The class description also includes information on how the character prepares spells each day.
Divine spells can be written down and deciphered just as arcane spells can (see Arcane Magical Writings, above). Any character with the Spellcraft skill can attempt to decipher the divine magical writing and identify it. However, only characters who are capable of casting the spell in its divine form can cast a divine spell from a scroll. (The character does not have to have the spell prepared; he or she only has to be capable of preparing and casting it in general.)
A psionic power is a one-time psionic effect manifested by a psionic character or creature. Psionic powers require power points to use, although naturally psionic creatures can manifest their powers a certain number of times per day with no power point cost.
Each psionic power is tied to a specific ability, which is the key ability for that psionic power. A psionic character must have a key ability score equal to at least 10 + the power's level to manifest a particular power.
Unlike arcane spellcasters, psionic characters don't have spellbooks and they don't prepare their powers ahead of time. A psionic character's level limits the number of power points available for manifesting powers. A psionic character has a set number of powers available that he may manifest at will, provided he has sufficient power points to pay for the manifestation.
A power manifests when the psionic character pays its power point cost. The character pays the cost, and the power manifests immediately.
Psionic powers don't require special gestures, words, or materials. They operate as thoughts made manifest. Most powers do have a noticeable display associated with their use, however.
Psionic advanced classes describe how many powers each class knows by level, as well as how many power points they have available each day.
To manifest a power, a character selects one power that he or she knows and pays the power point cost.
A power's cost is determined by its level, as shown below. Every power's cost is also noted in its description for easy reference.
* A psionic character can manifest any 0-level power he or she knows a number of times per day equal to 3 + his or her psionic level; additional manifestations cost 1 power point each.