Invocation Grade: Greater
Equivalent Spell Level: 6th
This eldritch essence invocation allows you to change your eldritch blast into a penetrating blast. A penetrating blast gains a +4 bonus on caster level checks made to penetrate a target’s spell resistance. A creature affected by a penetrating blast must succeed on a Will save or have its spell resistance lowered by 5 for 1 minute. Multiple uses of this essence don’t stack; instead, the new duration replaces the old one.
Source: Dragon Magic, page 82.