Identifying Spells

Noticing a Spell Being Cast

Manifesting and expressing magic is not normally an inconspicuous process. The casting of a spell is perceptible to any creature in the immediate area as long as it involves any components whatsoever. Verbal components usually involve loud and forceful incantations, somatic components include broad and precise gestures, material components may be odd, large or cumbersome, and a spellcasting focus may glow, vibrate, or change color during the casting of a spell.

Even a hidden creature will reveal itself the moment it begins utilizing the components of a spell.

Imperceptible Casting

The only way that the casting of a spell can be hidden is if the need for a spell's components has been removed by a special ability, such as the sorcerer's Subtle Spell feature. In such cases, the casting of the spell is imperceptible.

Perceptible Spell Effects

An effect like crackling lightning is obvious, a creature experiencing such an effect knows that something is happening to it, though it may not necessarily know that the effect is magical depending on the circumstance. If an imperceptible casting produces a perceptible effect, it's normally impossible to determine who cast the spell in the absence of other evidence.

Imperceptible Spell Effects

If a spell has an imperceptible effect, a creature might not know it was targeted by a spell at all. A more subtle effect, such as an attempt to read a creature's thoughts, typically goes unnoticed, unless the target is able to perceive the spellcaster at work or the spell itself indicates that the target is aware.

Identifying a Spell

Sometimes you might want to identify a spell that someone else is casting or that was already cast. To do so, you can use your reaction to identify a spell as it's being cast, or you can use a bonus action on your turn to identify a spell by its effect after it is cast.

If you perceived the casting, the spell's effect, or both, you can make an Intelligence (Arcana) check with your reaction or bonus action on your turn. The DC equals 15 + the spell's level. If you have the spell memorized or among your spontaneous spells, you automatically know what the spell is, no reaction or bonus action required.

This Intelligence (Arcana) check represents the fact that identifying a spell requires a quick mind and familiarity with the theory and practice of casting. This is true even for a character whose spellcasting ability is Wisdom or Charisma. Being able to cast spells doesn't by itself make you adept at deducing exactly what others are doing when they cast their spells.