A spell is a one-time magical effect. Spells come in two types: arcane (cast by bards, sorcerers, and wizards) and divine (cast by clerics, druids, and experienced paladins and rangers). Most spellcasters prepare their spells in advance - whether from a spellbook or through devout prayers and meditation - while some cast spells spontaneously without preparation. Despite these different ways that characters use to learn or prepare their spells, when it comes to casting them, the spells are very much alike. Cutting across the categories of arcane and divine spells are the eight schools of magic. These schools represent the different ways that spells take effect.
All spellcasters draw from a pool of existing spells available to them. Each day, they prepare a subset of those spells. Throughout the day, they cast these spells by expending spell slots. These spell slots are renewed daily. Each class gains spell slots at a different rate, acquiring higher level ones as they progress.
Each magic user has a pool of spells available to them. Each class collects spells in these pools in a different way. Wizards, Magi, and Alchemists copy spells into spell or formulae books (see Spellbooks below). Each day, they prepare a set number of spells from those they have transcribed. As they adventure, their repertoire of spells continues to grow. Intuitive casters, such as bards, inquisitors, and sorcerers, have a set list of spells that they always intuitively know--no spellbook needed. They don't need to prepare spells each morning, but the range of spells they can use is limited. Other casting classes prepare spells each day, but they are free to prepare any spell available to them. Some of these classes (Rangers, Witches, and Oracles) use a standard spell list that is the same for any character in that class. Others (Druids, Paladins, Clerics) have custom spell lists that are defined by the domains to which they have access (see domains below).
Some classes have to take time each day to prepare the spells they plan on casting. They select these spells from the pool of those available to them. The number of spells they can prepare is as follows.
Prepared Spells = 2+ Caster Level + Casting Ability Bonus
Wizards, magi, witches, and alchemists must take an uninterrupted long rest before preparing new spells. Afterwards, they need one hour of quiet study to choose their spells for the day. They choose this list of spells fresh each time, clearing out any old, unused spells.
Clerics, oracles, and other domain-based spellcasters do not need a long rest. Instead, they simply perform a daily ritual (at the same time each day) to cleanse their minds and receive new spells. This ritual takes one uninterrupted hour as well.
Bards, sorcerers, and inquisitors do not need to prepare spells they need for the day, though they need 15 min of meditation in the morning to make sure their minds are fresh.
Some spellcasters become very proficient with certain spells, and eventually they no longer need to prepare some of these. For instance, Druids automatically get spells through Summon Nature's Ally. These spells don't count toward your total number of prepared spells in a day. However, they do still require you to expend a spell slot when cast.
Each spellcaster has a certain number of spell slots available to them. As the spellcaster levels up, higher level spell slots become available and the caster gains more low-level slots. When casting a spell, the caster must have an appropriate spell slot available for the spell to work. All spells have a minimum slot level needed to be cast, though many can be leveled up by casting them at higher levels, increasing the potency of the spell. After casting the spell, the spell slot used is expended, though the spell still remains prepared for re-use, if necessary.
Certain spells are marked as ritual spells in their casting time. Optionally, these spells can be cast without expending a spell slot. This version takes 10 minutes longer than usual and cannot be cast at a higher level. Ritual spells still need to be prepared, as usual, before being cast.
First, you must choose which spell to cast. If you're a cleric, alchemist, druid, magus, experienced paladin, experienced ranger, witch, or wizard, you select from among spells prepared earlier in the day. If you're a bard, sorcerer, inquisitor, or oracle you can select any spell you know.
To cast a spell, you must be able to speak (if the spell has a verbal component), gesture (if it has a somatic component), and manipulate the material components or focus (if any). Additionally, you must concentrate to cast a spell. Some spells have an experience point cost needed to cast (noted as an XP component). Unless otherwise stated, each casting of these spells costs the caster 1 XP.
If a spell has multiple versions (or is reversible), you choose which version to use when you cast it. You don't have to prepare a specific version of the spell. If a spell has multiple levels, you choose the level to cast at (provided you have a spell slot open).
Cantrips are minor spells that most spellcasters learn as their magical powers grow. As a wizard you may have learned a few cantrips during your apprentice days, the first simple magics you were able to do. Or maybe as a sorcerer your cantrips were the first inking that something was special about you--the minor powers you accidentally started to manifest one day. Regardless of backstory, all casters except for rangers, paladins, and alchemists know cantrips.
You start at level 1 by knowing three cantrips of your choice. Choose cantrips that fit your backstory or ones that feel appropriate to your character's unique talents. Once chosen, you generally don't switch your cantrips, though your GM may make an exception, as usual. As your level up, you pick up a few more cantrips, learning a new one at level 5 and every five levels afterward.
Cantrips are cast like normal spells. They all take a standard action to do so, but they don't require spell slots and can be cast as many times as you wish. Cantrips also function as normal spells in that they can be dispelled, countered, or suppressed like all magic. All cantrips use verbal and somatic components. Cantrips also cannot deal damage or affect the concentration of spellcasters. They also cannot replicate the effects of any other spell.
Some level 1 spells can be downcast to a level 0, allowing you to cast them as a cantrip. Not all spells can be cast this way; those than can have a cantrip field in their spell blocks. To cast a spell as a cantrip, you must have it prepared, though like all cantrips casting the spell this way requires no spell slots. The level 0 effect of a spell is usually a minor, less-potent version of the level 1 ability.
There are three types of spells--target, effect, or area--and each uses a different method of aiming. With target spells, you simply pick a target for the spell, with effect spells you pick a location where the effect happens, and with area spells you pick a location to center or start the area effect. Regardless of how you aim, you need to be able to see your target and have a straight, unblocked path from you to it.
Some spells have a target or targets. You must be able to see or touch the target and have an unblocked path to it. If the target is willing, the spell is automatically successful. If not, you may need to make a spell attack to hit them, or they may need to make a saving throw to avoid it. Spells against unconscious creatures are automatically successful.
Some spells create or summon things. You must designate an area or location for these things to appear and be able to see an unblocked path to this point. Some effects create rays, bolts of energy, or other effects that shoot from you like a ranged weapon. These effects can be fired blindly at a target without seeing exactly where it is, though you still need to pick a square to target and make a 3/4 cover check.
Some spells affect an area. You must select a point where the spell originates. You must be able to see this point and have an unblocked path between you and it. All creatures in the specific area are affected by the spell. Most spells that affect an area have a particular shape and size (cone, cylinder, line, or sphere). Lines occupy a space 5' wide and extend for a certain distance. Cones create a shape 90 degrees wide for the specified distance.
Some area spells have an effect that starts at a specific space and moves in a particular direction. These are usually described as having a burst or emanation (instead of spread). Such spells require line of effect to hit a creature--an unbroken, straight line from the start of the effect to a creature affected by it. An opening smaller 1 square foot usually still blocks line of effect.
Some spells automatically hit one or more creatures in range, though these targets have a chance to make a saving throw against its effects. These may be creatures that you directly target or ones that are in an area of effect. The type of save required will be outlined in the spell description. The target of the spell will make a saving throw against the caster's Save DC (see Combat).
Some spells shoot a ray, magic bolt, or other magical effect at your target. With these attacks, you roll a spell attack instead against your target's standard AC to hit it. Like a melee or ranged attack, spell attacks can be modified by effects that enhance your attack rolls, but they also suffer the same drawbacks of normal attacks (cover checks, disadvantage against prone targets, etc.). Likewise, they automatically miss on a critical fail and automatically hit on a critical hit, doubling damage as usual.
For some spells, like dispel magic, you also make a spell attack check to overpower the effects of another spell caster, to break through spell resistance, or to cancel other magical effects. These are mental attacks where you use your arcane expertise to bend magic to your will. Generally, effects that modify normal attack rolls don't apply to these kinds of checks.
To make a spell attack, roll a d20 and add your spell attack bonus plus any modifiers. Your spell attack bonus is calculated as follows. If you have levels in multiple spellcaster classes, use the highest casting ability bonus.
Spell Attack Bonus = Your character level + your casting ability bonus.
Some spell effects require you to touch a target to affect it. To do so, roll a Spell Attack (plus any attack modifiers) against your target's touch AC. If you fail to touch your opponent, your spell is not expended, and you may hold the charge for another attempt next round. This requires concentration and the spellcaster must release any other concentration spells he is maintaining. The GM may also rule that other conditions cause you to lose the charge as well.
Touch spells may be made up close (melee) or at a distance (ranged). A touch spell that deals damage can score a critical hit just as a weapon can, dealing double damage. Some touch spells allow you to touch multiple targets. You can touch as many willing targets as you can reach as part of the casting, but all targets of the spell must be touched in the same round that you finish casting the spell.
With some spells, you conjure an object then throw it at your opponent. Although, it might seem like these are spell attacks, the spell's effect is to create the object, not propel it. To make the actual attack, you usually make a normal ranged attack, though usually you can do so in the same action as casting the spell. Some of these spells create bomb-like objects (like produce flame or snowball). These bombs only need to touch your target to have an effect, so they hit against the target's touch AC. The spell description will distinguish which type of attack you need to make.
There are three types of concentration that come into play while spellcasting. First, to cast a spell, you must concentrate. Second, some spells stay in effect while you consciously focus on them (Duration: maintained concentration). With these spells, you typically must use your standard action each round to continue to focus on the spell. As soon as you stop a conscious effort to maintain the spell, its effects start to fade. Third, many spells require a minor amount of subconscious concentration (Duration: Concentration) to remain in effect. The concentration for these is minimal and is maintained intuitively in the back of your mind while engaging in other activities (talking, fighting, etc.). You may even consciously concentrate on other tasks, such as spell-casting, provided those spells don't have a concentration duration as well. As soon as you cast a new concentration spell, your old one is lost.
All three types of concentration can be interrupted causing the spell to fail. If the spell fails during spellcasting, it fizzles before effects can take place.
Injury: If you take damage while concentrating, you must make a CON save (DC = points of damage taken). If you fail the check, you lose the spell without effect. The interrupting event strikes during spellcasting if it comes between when you start and when you complete a spell, if it comes in response to your casting the spell, of if you are taking continuous damage.
Spell: Some spells are designed to be distracting. If you are affected by one of these spells while attempting to cast a spell of your own, you must make an INT or CON save or lose the spell you are casting (against the Spell Caster DC). INT saves are typically made for mental distractions, CON for physical ones.
Grappling: While grappled, you are still able to cast spells, though you must make a CON save (DC 15 + the level of the spell you're casting) or lose the spell. In certain grapples, the GM may rule that you can only use spells where the material components in-hand or easily available, especially if you do not have the freedom to easily dig through your gear to find them. After you are restrained (level 3), 'you can no longer cast spells with somatic, material, or focus components.
Vigorous Motion: If you are riding on a moving mount, taking a bouncy ride in a wagon, on a small boat in rough water, below-decks in a storm-tossed ship, or simply being jostled in a similar fashion, you must make a CON save (DC 15 + the level of the spell you're casting) or lose the spell.
Lack of Attention: Any state of mind where mental function is no longer consciously controlled causes the spell to automatically dissolve (including unconsciousness, death, petrification, sleep, etc.).
It is possible to cast any spell as a counterspell. By doing so, you are using the spell's energy to disrupt the casting of the spell by another character. Counterspelling works even if one spell is divine and the other arcane. To counterspell, you must be able to see the other spellcaster and be aware that he is spellcasting. As such, spell-like effects, supernatural abilities, and spells that are made silent and still through metamagic techniques, cannot be countered. There are two ways to counterspell, by casting the same spell or by casting dispel magic as a reaction.
Casting the Same Spell: To use a counterspell, you must select an opponent as the target of the counterspell. You do this by choosing the ready action. In doing so, you elect to wait to complete your action until your opponent tries to cast a spell.
If the target of your counterspell tries to cast a spell that you are able to cast, you automatically identify it. Otherwise, make an Arcana check (DC 15 + the spell's level). This check is a free action. If the check succeeds, you correctly identify the opponent's spell and can attempt to counter it. If the check fails, you can't do either of these things.
To complete the action, you must then cast the same spell, negating both. Counterspelling in this manner is more difficult, but it always succeeds, even if you cast the spell at a lower level than your opponent.
Dispel Magic as a Counterspell: You can use dispel magic to counterspell another spellcaster, and you don't need to identify the spell he or she is casting. You choose which level to cast dispel magic at and spells of that level and lower are automatically dispelled. If the spell is at a higher level, you must make an opposed spell attack against the caster.
Spells or magical effects usually work as described, no matter how many other spells or magical effects happen to be operating in the same area or on the same recipient. Except in special cases, a spell does not affect the way another spell operates. Whenever a spell has a specific effect on other spells, the spell description explains that effect. Several other general rules apply when spells or magical effects operate in the same place:
Stacking Effects: Spells that provide bonuses or penalties on attack rolls, damage rolls, saving throws, and other attributes usually do not stack with themselves. More generally, two bonuses of the same type don't stack even if they come from different spells (the stronger usually winning out). Effects that target different abilities or scores, will likely stack.
Spells with Opposite Effects: Spells with opposite effects apply normally, with all bonuses, penalties, or changes accruing in the order that they apply. Some spells negate or counter each other. This is a special effect that is noted in a spell's description.
Instantaneous Effects: Two or more spells with instantaneous durations work cumulatively when they affect the same target.
Some conditions of magical effects allow you to cast enhanced spells, usually at one level higher than normal. This means you are able to cast a spell as if it were cast from a spell slot one level higher than the one that you use (e.g. an enhanced 2nd level spell functions as a 3rd level spell).
Some spells change effects at higher levels (like cloud). Enhanced versions of these spells don't change effect, but still function as if they were the lower level (e.g. an enhanced 2nd level cloud spell still functions as fog cloud).
Spells that increase in potency when cast at higher levels are affected by enhanced casting. So, an enhanced 3rd level Lightning Bolt spell will deal 9d6 points of damage, not 8d6. Furthermore, enhanced spells can be used with metamagic techniques. So, you could use extend spell on an enhanced 2nd level spell to double its duration without having to expend a 3rd level spell slot.