The Lightning Elemental appears as a cloud of soft light, steady. There is a definite core, which is very small, surrounded by rotating arcs of electric energy. The stronger the elemental, the larger, and greater in number these arcs appear. Thus a weak elemental might put off no more light that a dim lightbulb, with a single arc chasing around it, an elemental lord of lightning could be seen for miles, and have dozens of arcs chasing around it's core. There will be fairly regular discharges of mundane electricity from the elemental to grounded objects, and metal objects will also draw this sparking.
Illumination - lightning elementals dispell darkness and shadow based magics by proximity. Illusion and misdirection spells also must save or be destroyed. Incorporeal and invisible creatures are rendered visible.
Blink - lightning elementals can jump almost anywhere in a combat zone and engage in close quarters fighting.
Invulnerable - cannot be confused, mind controlled, critically hit, intimidated, seduced, petrified, stunned, and so forth.
Basic attack - proximity spark - deals damage as a javelin plus an equal amount of electrical damage. Larger elementals can perform multiple attacks.
Greater attack - greater proximity spark - deals damage as a ballista, plus equal amount of electrical damage, with knock back/knock down check.
Bolt - deals dagger damage plus equal amount electrical. Small elementals are often limited to either Bolt or proximity attack, medium elementals can do both.
Bolt 2 - deals sword damage plus equal amount electrical.
Bolt 3 - deals greatsword damage plus equal amount electrical
Bolt Storm - limited to large and above elementals, bolt storm deals 1d4 Bolt 3 strikes, 1d6+1 Bolt 2 strikes, and 1d10+2 Bolt 1 strikes against a group of foes. All in the area of attack must make save checks to avoid being temporarily blinded, stunned, or knocked unconscious by this vulgar display of power.