Force Lightning

was a well known dark side Force ability.

It was a purely energy-based attack used most commonly by, but not restricted to, the Sith. Force energy took the form of lightning bolts which exit the Force-user's body through his fingertips or palms; Force lightning could be executed with either one or two hands. The greater the user's aptitude, the more power the lightning bolts possessed and the more they forked, allowing the possibility of striking multiple foes at once. This Force power was often used as a form of torture as it not only caused severe physical damage but also extreme agony to the victim's emotional and spiritual capacities. However, a single powerful blast may have been sufficient to kill a person instantly. It is unclear why Palpatine kept electrocuting Luke Skywalker for so long, but it is likely that Palpatine, harboring extreme antipathy toward the Jedi, sought to maximize the intensity and duration of Luke's suffering in order to satisfy himself with the tormenting of the last of their kind.

The intensity varies based on a number of factors, but a skilled user can render a target unconscious with only a short burst. Depending on the level of intensity, Force lightning could apparently ground itself on an ignited lightsaber. Strong lightsiders are sometimes able to resist Force lightning, and it can also be blocked with a lightsaber. Mace Windu, with his lightsaber combat form Vaapad, could reflect the lightning back to its source with the concept of a "superconducting loop". Nevertheless, a sufficiently powerful Force-user could blast through the defenses afforded by a lightsaber, as seen when Darth Sidious blasted Grand Master Yoda's lightsaber right out of his hand during their duel in the Senate chamber. Force lightning could also be absorbed and redirected by a Jedi of sufficient skill; Yoda demonstrated this ability by both reflecting and absorbing it during a fight with Count Dooku.

It is thought that very intense use of Force lightning could drain the user physically, and possibly result in severe facial and body deformations. This is considered by some to have been shown when Darth Sidious unleashed a barrage of Force lightning on Mace Windu, but it reflected back upon him by the Jedi Master's lightsaber. Nevertheless, this view is controversial; it is thought by some that Sidious's physical appearance as Chancellor Palpatine was an illusion created with Force energy, or a physical form of concealment, and that the lightning merely melted it away.

Deformities like the Chancellor's—to lesser extent—have been the product of intense use of the Force and long-time immersion to the dark side, so perhaps the lightning did not actually cause the transformation. Testament to this are the bloodshot yellow eyes, rotten teeth and sharp, dirty fingernails that replaced the Chancellor's clear blue eyes and healthy teeth after the lightning was redirected to him. Nevertheless, it is clear that Palpatine's lightning caused him some physical damage, external or internal, though to what extent is unknown.

Besides draining the user's energy, Force lightning had the added drawback of occasionally charring the hand of the person who used it. When Jacen Solo flew into a rage underneath the ruins of the Jedi Temple on Yuuzhan'tar and attacked his Yuuzhan Vong pursuers with Force lightning, he later found that the blasts had burned charred holes in his palm. However, unlike other users of Force lightning, Jacen was untested with the ability, and it is possible that Force users more experienced with the technique can prevent this. It is also possible that the sheer intensity with which Jacen lashed out at his attackers caused the power to exceed his capacity to restrain it, which could also explain why he fell unconcious immediately after using the ability.

Following Palpatine using Force lightning on Luke Skywalker it was found that his bones had undergone calcification and he was forced to rest for a number of days until his bones returned to normal status. Count Dooku's brief barrage on Anakin Skywalker also charred Anakin's body a bit, and when his robes had been taken away for laundry, droids discovered several charred holes blasted through the robe.

Information courtesy of Wookiepedia