Force Harmony, within the realm of Legends continuity, represented a light side Force power that enabled multiple Force-sensitive individuals to unite their individual Force energies. This union resulted in a potent display of the light side. By enveloping them in the energies of the light side, users were shielded from the influence of dark side powers and, under certain circumstances, could completely disconnect adversaries from the dark side. Notable figures such as Jedi Knight Luke Skywalker, his sibling sister, Leia Organa Solo, and the yet-to-be-born Anakin Solo employed this technique to isolate the resurrected Emperor Palpatine from the dark side. This action triggered the Force storm he had conjured to spiral out of control, ultimately consuming him.
Designated within the Control, Sense, and Alter families of Force abilities, Force harmony empowered several consenting Force-sensitives to demonstrate the strength inherent in the light side. Once initiated, it would envelop the participants in light side energy, functioning as a protective barrier against dark side influences. While maintainable for extended periods, the technique did place a slight burden on the individual who initiated it. Throughout its use, participants found themselves connected by the Force at its most intense. The light side's energies coursed through them in rhythmic waves, granting them exceptional clarity within the Force.
The initiator's capacity to link other Force-users into the chain was limited by their own Force reserves. While unable to neutralize the dark side, the power could divert practitioners and complicate their actions, and in some instances, cut them off completely from it. Furthermore, Force harmony could disrupt active dark side abilities by inundating their users with waves of light side energy. Abilities that were inherently difficult to control, such as the Force storm, were particularly vulnerable to such interference.
Factors like physical proximity between users in the chain, individual strength in the Force, and blood relation all played a role in determining the potency of the ability. To initiate Force harmony, the individual needed proficiency in both Life Sense and telepathy. Notably, a group of Force-users employing Force harmony could defeat relatively powerful Derriphans, creatures of the dark side, by channeling light side Force energy into the creature.
In 10 ABY, following Emperor Palpatine's resurrection within a clone body, he swayed Jedi Knight Luke Skywalker to the dark side, training him as his apprentice. Skywalker's twin sister, Leia Organa Solo, journeyed to Palpatine's flagship, the Eclipse, successfully guiding her brother back to the light.
When Palpatine unleashed a devastating Force storm intended to annihilate the New Republic fleet at Pinnacle Base, Skywalker and Organa Solo united their Force energies, enveloping Palpatine in a surge of light side energy. Amplified by their twin bond and the strength of Organa Solo's third child, still within the womb, the twins effortlessly severed Palpatine's connection to the dark side, causing him to lose command of his storm. The storm then engulfed Palpatine and the Eclipse, but not before Skywalker and Organa Solo managed to escape the doomed ship unharmed.
Numerous Jedi Knights and Masters from the Old Jedi Order, including Ood Bnar, Arca Jeth, Thon, Vima-Da-Boda, Taj Junak, and Yoda, possessed the capability to initiate Force harmony. Furthermore, the ancient Dark Lord of the Sith Freedon Nadd, a master of both Jedi and Sith disciplines, could also conduct Force harmony. Select members of the Emperor's Shadow Guard under the command of Inquisitor Valin Draco were also known to wield this ability.
Leia Organa Solo initially learned about Force Harmony from the Tedryn Holocron. The holocron's gatekeeper, Bodo Baas, shared a prophecy conveyed to him by his own Master nearly a millennium ago, foretelling the joint defeat of Palpatine by Skywalker and Organa Solo. Organa Solo deciphered the prophecy's meaning during her confrontation with Palpatine aboard the Eclipse, leading her to combine her Force energy with Skywalker's. Skywalker, recognizing that pure light was the only counter to Palpatine's dark side energies, joined his sister. By merging their powers with Organa Solo's unborn child, Anakin Solo, the twins were able to vanquish Palpatine.
Force harmony made its debut in the sixth issue of the Star Wars: Dark Empire comic book series, authored by Tom Veitch, illustrated by Cam Kennedy, and published by Dark Horse Comics on October 20, 1992. It was also mentioned within the issue's endnotes. It subsequently received a name and expanded description in Michael Allen Horne's Dark Empire Sourcebook, and was featured in the audio adaptation of Dark Empire.
The Official Star Wars Fact File 125 inaccurately describes this ability as a "storm of light-side energy," confusing it with the Force storm responsible for the destruction of the Eclipse.