'CHAIN LIGHTNING'

This spell creates an electrical discharge that begins as a single stroke
of lightning, 2 feet wide, commencing from the fingertips of the caster.
Unlike a lightning bolt spell, chain lightning strikes one object or
creature initially, then arcs to a series of other objects or creatures
within range, losing energy with each jump.  Creatures immune to electrical
attack can be struck, even though no damage is taken.  Note that it is
possible for the chain to arc back to the caster!
 
See also: Lightning Bolt.