You can cast a spell such that it branches out to strike secondary targets.
Benefit: Spells affected by this feat must either have a target of one creature or object or an area of a single ray, cone, or line. When a chain spell strikes its first object or creature, it arcs to a number of secondary targets equal to your caster level (maximum 20), beginning with the closest possible target. If it the original spell requires a ranged attack roll, make a single roll and use this result for all targets. If the target of a chain spell avoids its effects due to spell resistance, a failed attack roll, or a successful save, the spell does not arc to further targets. A chain spell uses up a spell slot three levels higher than the spell’s actual level.
Feats 101. Copyright 2009, Steven D. Russell.