Magic and Spellcasting
Magic permeates the worlds of D&D and most often appears in the form of a spell.
A spell is a discrete magical effect, a single shaping of the magical energies that suffuse the multiverse into a specific, limited expression. In casting a spell, a character carefully plucks at the invisible strands of raw magic suffusing the world, pins them in place in a particular way, and then releases them to unleash the desired effect--in most cases, all in the span of seconds.
Spells can be versatile tools, weapons, or protective wards. They can deal damage or undo it, impose or remove conditions, drain life energy, or restore life.
The strength of a spell is indicated by its spell level. The higher a spell's level, the higher level a spellcaster must be in order to use that spell.
However, spell level and character level don't correspond directly. For example, typically a character must be at least 5th level to cast a 3rd-level spell.
Known and Prepared Spells
Before a spellcaster can use a spell, they must have the spell firmly fixed in mind. The number of spells a character can have fixed in mind depends on the class and the character's spellcasting ability modifier.
Clerics, druids, paladins, and wizards undergo a process of preparing spells. They can choose a specific number of spells from their entire class's spell list. They can change this list of prepared spells upon finishing a long rest.
All other spellcasters just have a certain number of spells memorized all the time. As the characters gain levels, they have the opportunity to switch out and learn new spells.
Manipulating magic and channeling its energy is physically and mentally taxing. Every caster has a limited amount of magical energy each day. The stronger (or higher level) the spell, the more magical energy it requires. A lower level spell can be cast at a higher level to make it stronger, but the opposite is not true.
Regardless of how many spells a caster knows or prepares, they can only cast a limited number of spells before resting. This is indicated by how many spell slots a character has for each level of spell. For example, at 3rd level, a wizard has four 1st-level spell slots and two 2nd-level spell slots.
When a character casts a spell, they expend a slot of that spell's level (or higher), effectively "filling" a slot with the spell.
Finishing a long rest restores any expended spell slots.
Other Spell Rules
There are two types of spells that utilize different rules: cantrips and rituals.
A cantrip is a spell that can be cast at will, without using a spell slot and without being prepared in advance. Repeated practice has fixed the spell in the caster's mind and infused the caster with the magic needed to produce the effect over and over.
A cantrip's spell level is 0.
Certain spells have a special tag: ritual. Such a spell can be cast following the normal rules for spellcasting, or the spell can be cast as a ritual. The ritual version of a spell takes 10 minutes longer to cast than normal, and it doesn't expend a spell slot.
Casting a Spell
There are a few basic rules to be aware of when casting spells. Every spell has a casting time, range, components, duration, and target.
Many spells require the caster to make an attack roll, just like when attacking with a weapon. It is a d20 roll + the caster’s spell attack bonus.
Some spells require the target to make a saving throw. Sometimes a target who succeeds on the saving throw completely resists the spell, other times they may just take a lesser effect.
It is possible to cast two spells in one turn, but one of them must have a casting time of a bonus action and the other must be a cantrip.
Most spells require a single action to cast, but some require a bonus action, a reaction, or much longer.
Bonus Action: spells that are especially swift. See note above about casting two spells in one turn.
Reactions: spells that take a fraction of a second to bring about and are cast in response to some event.
Longer: certain spells (including those cast as rituals) can require minutes or even hours. If you cast a spell with a longer casting time during combat, you must spend your action each turn casting the spell and must maintain your concentration.
The target of the spell must be within the spell’s range.
Most spells have ranges expressed in feet. If a spell effects only the caster it has a range of self.
The physical requirements you must meet in order to cast a spell.
Verbal (V) – most spells require the chanting of mystical words. A caster who is gagged or under a magical silence can’t cast a spell with a verbal component.
Somatic (S) – physical gestures from forceful gesticulations or intricate motions. The caster must have free use of at least one hand to perform these gestures.
Material (M) – particular objects. These are found in either a component pouch or can be substituted with the use of a spellcasting focus.
The length of time the spell persists, whether that is a specified number of rounds, minutes, hours, or even years.
Concentration: Some spells require you to maintain concentration. If you lose concentration, the spell ends.
There are a few things that can break concentration:
Casting another spell that requires concentration – you can’t concentrate on two spells at the same time.
Taking damage – you must make a Constitution saving throw. The DC equals 10 or half the damage you take, whichever number is higher. If you take damage from multiple sources, you make a separate saving throw for each source.
Being incapacitated or killed – automatically lose concentration
Most spells require you to pick a target. To target something, you must have a clear path to it. If you place an area of effect at a point that you can’t see and there is an obstruction, such as a wall, between you and the point, the point of origin comes into being on your side of the obstruction.
You can target yourself with a spell unless the spell description says otherwise.
Areas of Effect: Some spells allow you to target any creature within a specific area. Every area of effect has a point of origin, a location from which the spell’s energy erupts. A spell’s effect expands in straight lines from the point of origin.
A cone extend from the point of origin. A cube’s point of origin lies anywhere on a face of the cubic effect. A cylinder’s point of origin is the center of one of its circles. A line extends from point of origin in a straight path. A sphere’s point of origin is its center.