Some spells affect an area. The caster selects where the spell starts, but otherwise doesn’t control which creatures or objects the spell affects. Sometimes a spell describes a specially defined area, but usually an area falls into one of the following categories.
Burst: As with an effect, the caster selects the spell or power’s point of origin. The spell or power bursts out from this point, affecting whatever it catches in its area.
A burst spell has a radius that indicates how far from the point of origin the spell’s effect extends.
Cone: A cone shoots away from the caster in the direction he or she designates. A cone starts in a square adjacent to the caster and widens out as it goes. A cone’s width at a given distance from you equals that distance. Its far end is as wide as the effect is long.
Creatures: Some spells affect creatures directly (as a spell with a target does), but they affect creatures in an area of some kind rather than individual creatures the caster selects. The area might be a burst, a cone, or some other shape.
Many spells affect “living creatures,” which means all creatures other than constructs and undead.
Cylinder: As with a burst, the caster selects the spell’s point of origin. This point is the center of a horizontal circle, and the spell shoots down from the circle, filling a cylinder.
Emanation: Some spells have an area like a burst except that the effect continues to radiate from the point of origin for the duration of the spell.
Quarter-Circle: Some spells have a quarter-circle-shaped area. Like a cone, the effect starts in a square adjacent to the caster and widens out as it goes.
Spread: Some spells spread out like a burst but can turn corners. The caster selects the point of origin, and the spell spreads out a given distance in all directions. Figure distance by actual distance traveled, taking into account turns the spell effect takes.
Other: A spell or power can have a unique area, as defined in its description.
(S): If an Area or Effect entry ends with “(S)” (standing for “shapeable”), the caster can shape the spell. A shaped effect or area can have no dimension smaller than 10 feet.
Line of Effect: A line of effect is a straight, unblocked path that indicates what a spell can affect. A line of effect is canceled by a solid barrier. It’s like line of sight for ranged weapons, except it’s not blocked by fog, darkness, and other factors that limit normal sight.
A caster must have a clear line of effect to any target that he or she uses a spell on, or to any space in which he or she wishes to create an effect. The caster must have a clear line of effect to the point of origin of any spell he or she casts or power he or she manifests. For bursts, cones, cylinders, and emanation spells, the spell only affects areas, creatures, or objects to which it has line of effect from its origin (a burst’s point, a cone’s starting point, a cylinder’s circle, or an emanation spell’s point of origin).
A hole of at least 1 square foot is sufficient to allow a line of effect through an otherwise solid barrier. If any given 5-foot length of barrier contains such an opening, that 5-foot length is not considered a barrier for purposes of a spell’s line of effect (though the rest of the barrier still counts as normal).
Directing or Redirecting Effects: Some spells allow the caster to redirect the effect to new targets or areas after casting the spell. Redirecting a spell requires a move action that does not provoke attacks of opportunity. It also doesn’t require concentration.