The Second Battle on Onderon transpired during the Freedon Nadd Insurrection in the year 3998 BBY. This conflict arose from the Galactic Republic's Military involvement, which was requested by Tchuukthai Jedi Master Thon. Thon, accompanied by his Padawan Nomi Sunrider, attended a Galactic Senate Defense Ministry session. The purpose of this session was to discuss the escalating dark side threat on Onderon. Ultimately, Sunrider was selected to command the Republic's naval forces against the followers of Dark Lord of the Sith Freedon Nadd. These followers were unified under the leadership of Onderon's monarch, King Ommin.
Arriving in Onderonian space with a full Republic Navy escort, Nomi Sunrider, along with a team of four other Jedi Knights, confronted Ommin and his Naddist army. The battle began just as Tetan aristocrats Satal and Aleema Keto reached Onderon, seeking to interpret an ancient Sith grimoire. Caught amidst the fighting, the Ketos' ship was destroyed, crashing in Iziz. After searching, they found Ommin, who introduced them to Sith knowledge. Before Ommin could initiate their Sith training, the Jedi Knights ambushed them. The Jedi prevailed against the sorcerer King, rescued the captured Jedi Master Arca Jeth, defeated Ommin's forces, and liberated Onderon from Nadd's dark influence. The Ketos also fled Onderon, and, equipped with Sith relics, became Nadd's new Sith pupils.
In 4000 BBY, Jedi Master Arca Jeth, with his three apprentices, acting as sentinels of the Onderon system, discovered the dark side influencing the planet of Onderon. Over the subsequent two years, the Jedi uncovered that the Onderonian royal lineage had maintained the legacy of the deceased Sith Lord Freedon Nadd. Consequently, the Jedi became embroiled in conflict against Onderon's rulers and their Naddist adherents. Recognizing the threat exceeded their capabilities, Jeth requested aid from the sentinel of the Stenness system, the Tchuukthai Master Thon. Thon readily agreed, dispatching his student Oss Wilum to assist Jeth and his apprentices with the Onderon uprising. However, Thon also believed it was necessary to seek intervention from the Republic. Traveling to the galactic capital, Coruscant, with his new protégé, Nomi Sunrider, Thon attended an ongoing session of the Galactic Senate's Ministry of Defense.
The senators had recently received a distorted distress signal sent to Coruscant by Jedi Knight Ulic Qel-Droma. This prompted a vigorous debate among the senators regarding whether to provide aid to Onderon or allow the Jedi to manage their own affairs. Thon and Sunrider entered the Grand Convocation Chamber, where, with Sunrider translating his native Tchuukthese, Thon addressed the Senate.
Thon urged the assembly to assist the Jedi, reminding them of the Order's long-standing support of the Republic and warning that the dark side's conquest of Onderon would spread throughout the galaxy. The Jedi Master also revealed a surprise for his apprentice. Sunrider learned that Onderon would be her first mission as a Jedi, joining her fellow Knights. Thon's compelling pleas swayed the senators, and Sunrider was chosen to lead the full force of the Galactic Republic Navy against Freedon Nadd's followers without delay.
Around the same time, two young nobles from the Empress Teta system arrived on Coruscant. Satal Keto and his cousin, Aleema, heirs to the Tetan Monarchy, visited Coruscant's Galactic Museum in pursuit of dark side knowledge. They pilfered a Sith spellbook from an exhibit and returned to their lodgings, only to discover they could not decipher its text. However, the Ketos' hopes were rekindled upon hearing a news report about Dark Side Adepts on Onderon who practiced ancient Sith magic. Realizing Onderon was their best chance to unlock the book's secrets, they immediately departed for that planet.
Back on Onderon, the Jedi and drexl-mounted Beast Riders from the planet's wilderness engaged in intense combat with the Naddists in the capital city of Iziz. Arca Jeth, Ulic Qel-Droma, and Queen Galia, the daughter of the Onderonian ruler, the Sith sorcerer King Ommin, located the King and his Dark Side Army in the catacombs beneath the Royal Palace, where Master Jeth confronted him near Freedon Nadd's sarcophagus. Ommin revealed his long-standing alliance with Nadd's ghost, as the Dark Lord's specter materialized behind him. Nadd then commanded the armored Dark Jedi Warb Null to engage Qel-Droma, but the duel was merely a deception orchestrated by the Dark Lord and Null's Master, Ommin. The true target was Arca Jeth, whom Ommin attempted to capture while Qel-Droma and Null battled.
Newly empowered by Nadd's sudden arrival, Ommin captured Jeth and dragged him deeper into his lair's catacombs. Qel-Droma defeated Null but was unable to rescue Jeth. Realizing that pursuing the King was futile, Qel-Droma and Galia escaped the tunnels, closely followed by a contingent of her father's Dark Side Army. Emerging aboveground, they found the battle in full swing, where they encountered Jedi Tott Doneeta, who escorted Galia to the Nebulon Ranger while Qel-Droma met with his brother Cay and Galia's new husband, the Beast-Lord Oron Kira.
Kira, the Beast Riders, and the remaining Jedi had been fighting the Naddists for two days. The enemy had retaken the palace, and Kira was preparing to retreat to his fortress when Ulic Qel-Droma arrived. Qel-Droma had sent a distress call to the Republic in hopes of reinforcements, though he was unsure if it was received. Determined to rescue Jeth from Ommin's grasp, but surrounded by Naddists, the Jedi Knights and Oron Kira's forces had only one option: to survive until reinforcements arrived.
As Sunrider and the Republic Navy entered Onderonian space, they initiated their orbital attack run, preparing to deploy ground forces and air-to-ground troops. While the generals finalized their plans, an unidentified civilian yacht of Tetan origin exited hyperspace amidst the Republic Navy's bombardment. Despite warnings to avoid the restricted military zone, the civilian craft ignored the Navy's commands and headed straight for the planet.
As Republic rocket-jumpers commenced their air-to-ground assault over Iziz, the civilian vessel, carrying the Ketos, was caught in the crossfire and crashed. The Ketos survived the crash and sought out practitioners of the dark side, who brought them before Ommin.
Meanwhile, a team of Jedi Knights, including Dace Diath, Qrrrl Toq, Shoaneb Culu, and Kith Kark, arrived on Onderon with Sunrider to aid Oss Wilum, Tott Doneeta, Ulic and Cay Qel-Droma, who were trapped inside Kira's forest citadel, under heavy fire from the Naddist armies. Sunrider's Jedi team created a Force barrier as they fought towards their besieged comrades, and Sunrider used her battle meditation to shift the battle's momentum. Sunrider's meditation skills proved invaluable, restoring the Jedi's fighting spirit, though Kark was killed by Naddists, becoming one with the Force.
The Jedi were also affected by the suppression of the dark side in the Onderonian atmosphere, which diminished their connection to the Force. Sunrider traced the source to an old, incapacitated man focusing his dark power nearby. The old man sensed the novice Jedi's probe and retaliated with the dark side, knocking Sunrider off her feet. Ulic Qel-Droma rushed to her side, their first meeting. Qel-Droma, alarmed by the fallen Jedi, discovered that the old man was King Ommin, who ruled Onderon with Sith magic and held Jeth captive. Gathering the other Jedi Knights, Qel-Droma led them through the tunnels beneath the palace to Ommin's lair.
Simultaneously, the Ketos met with the crippled Ommin, who relied on a steel exoskeleton for support. Satal presented the stolen Sith spellbook, asking Ommin to translate it. Ommin provided an ancient Sith amulet, received from Freedon Nadd, enabling Satal to easily understand the ancient writings. Ommin then gave the book to his assistant Novar for duplication.
As Novar transcribed the book, Ommin revealed his "most prized possession" to the Tetan heirs: a Jedi Master, hanging on the wall, tortured by Sith magic. Aleema was horrified as Ommin explained his plan to corrupt Jeth with the dark side and transform him into a Dark Jedi. Ommin leaned close to Jeth, who whispered that his time was near and his Jedi Knights had arrived.
On cue, seven Jedi Knights stormed Ommin's lair, destroying numerous Sith Elite Warbots. During the skirmish, Cay Qel-Droma was attacked and lost his droid arm. The Jedi pressed on, surprising Ommin and the Tetan visitors. Ommin proved a formidable foe, blasting Sunrider and Ulic Qel-Droma with dark side energy. Before he could attack again, Qel-Droma slashed through Ommin with his lightsaber, causing him to collapse. Novar perished, caught in the ambush before completing the spellbook transcription. Satal and Aleema Keto escaped into the tunnels amidst the chaos.
The Ketos retreated deeper, encountering Freedon Nadd's spirit, who gifted them Sith artifacts, including their book and two Sith swords that belonged to Ommin. Nadd declared them heirs to a great Sith destiny, promising to guide their dark side instruction. He directed them to an exit, and the Ketos escaped unharmed.
Nadd appeared beside Ommin, whose life support had been destroyed, leaving him helpless. The Jedi had rescued Jeth, leading Nadd to realize Ommin's failure. Nadd withdrew his power, reminding Ommin that the Jedi did not belong to the dark side, though he speculated that some might fall. Jeth denounced Nadd as Ommin died and congratulated Qel-Droma. Nadd laughed, claiming the Jedi had lost, a truth they would soon realize.
As the Republic imposed martial law on Onderon, off-worlders were evacuated to their homeworlds. Customs personnel were ordered to prevent the smuggling of dark side weaponry, but Satal and Aleema Keto blended in and slipped through checkpoints.
The sarcophagi of King Ommin, his wife, Queen Amanoa, and Freedon Nadd were transported to the far side of the Dxun moon, as planned before the Naddist Uprising. Jeth had cleansed Onderon, and the natives began rebuilding their war-torn civilization. With Ommin gone, Oron Kira and Galia could peacefully rule as King and Queen of Iziz.
The Jedi enjoyed a brief respite, learning to ride Beast-Riders' mounts. However, Jeth remained concerned about the Tetan nobles' dark side curiosity. Hearing news of a recent political uprising in the Empress Teta system, the Jedi Master suspected Sith magic had survived and reached the Tetan worlds. Jeth accepted responsibility for Empress Teta, preparing his Jedi to confront the dark side again.
Freedon Nadd's prophecy, that some of the Jedi would fall to the dark side, came true. Of the eight surviving Jedi Knights, two aligned with the Sith. Ulic Qel-Droma defected and joined the Ketos' Sith-inspired Krath, becoming a Dark Lord. Oss Wilum was seduced by Dark Lord of the Sith Exar Kun and possessed by a dark side spirit within Kun's stolen Sith holocron.
The Second Battle of Onderon debuted in Freedon Nadd Uprising 2: Initiates of the Sith from the Tales of the Jedi comic series. The battle was created and written by Tom Veitch and drawn by Tony Akins. Veitch was initially contracted for a "one-shot deal" by Dark Horse Comics, resulting in The Freedon Nadd Uprising. Later, Veitch and Kevin J. Anderson used the battle and the Uprising as background for Dark Lords of the Sith, exploring Aleema and Satal Keto in depth. The battle also serves as a backdrop for the Krath Holy Crusade, part of the larger Great Sith War. The battle was recounted in the Tales of the Jedi audio drama, written by John Whitman and based on Veitch's script.
In the original comic, Nomi Sunrider is on Ossus when chosen to lead a Jedi team to aid Arca Jeth's Knights. She arrives on Onderon with Dace Diath, Shoaneb Culu, Kith Kark, and Qrrrl Toq. In the audio version, Sunrider accompanies Thon to Coruscant, bypassing Ossus, and is chosen to lead the Republic Fleet, not the Jedi. The other Jedi Knights from the comic were not mentioned in the audio drama.