Personal Lightning Caster is a projectile modifier that causes its projectile to "infect" a creature with the Personal Lightning Caster effect, making strike out with Lightning Bolts in random directions until it dies. If the projectile can strike you, either by enemy wand use or friendly-fire projectiles, it will affect you as well.
Like Personal Fireball Thrower and Personal Tentacler, the effect lasts for 83 seconds, assuming the entity affected by Personal Lightning Caster can survive that long. This timer is reset if the entity polymorphs.