Eldritch Chain

Warlock Invocation
Level: Lesser, 4th lv.
Components: V, S
Casting Time: 1 standard action
Range: 60 feet+30feet between targets
Duration: Instant
Saving Throw: None
Spell Resistance: Yes

This blast shape invocation allows you to improve your eldritch blast by turning it into an arc of energy that “jumps” from the first target to others. An eldritch chain can jump to one or more secondary targets within 30 feet of the first target, allowing you to make additional ranged touch attacks and deal damage to the secondary targets if you hit.
You can “jump” the chain to one secondary target per five caster levels, so you can strike two additional targets at 10th level, three additional targets at 15th level, and four additional targets at 20th level. Each new target must be within 30 feet of the previous one, and you can’t target the same creature more than once with the eldritch chain. If you miss any target in the chain, the eldritch chain attack ends there.

(Complete Arcane, Page 133)