In 990 BBY, the Anti-Republic Liberation Front, a terrorist group, made an attempt to abduct Tarsus Valorum, the former Supreme Chancellor. This occurred while Valorum was undertaking a diplomatic mission to the planet of Serenno. The Lethan Twi'lek Kelad'den led the group, killing servants from House Nalju of Serenno and replacing them with their own operatives. Upon arrival at a remote landing pad provided by the House, Cyndra, a Chiss female, detonated explosives as Valorum and his guard disembarked. This destroyed the former Chancellor's ship and resulted in the deaths of the entire crew. Johun Othone, a Jedi who volunteered to protect Valorum, defended the former chancellor from the assassins.
Othone swiftly eliminated two Human assassins, and Kelad'den killed a third as he tried to escape the conflict. After Cyndra and Paak fled, the Twi'lek warrior remained as the sole opponent, engaging Othone in a duel. Despite Kelad'den's initial advantage, the Jedi Knight ultimately chose to sacrifice himself for the former Chancellor, plunging himself and the Twi'lek off the fifty-meter-high platform.
Although Kelad'den's neck was broken in the fall, Othone survived because of the Force. In gratitude, Valorum honored Othone's request by appealing to the Galactic Senate to establish a memorial for all the Jedi who perished in battle on Ruusan.
In the year 990 BBY, Darth Zannah, a Sith Lord, was dispatched by her Master, Darth Bane, to the planet of Serenno. Her mission was to create discord, diverting the Galactic Republic from the subtle schemes of the Sith. The Sith apprentice cultivated connections, seducing Kelad'den, a red-skinned Lethan warrior Twi'lek, over several months. She posed as Rainah, an employee of the Republic embassy. Zannah was aware of the Twi'lek's involvement in a small, radical anti-Republic faction and intended to exploit this for the Sith's benefit.
She persuaded Kelad'den to take her to a gathering of the group, known as the Anti-Republic Liberation Front, with the goal of gaining control over them. The Twi'lek delivered a speech at the meeting, largely using words provided by Zannah. The Sith relied on Kelad'den's eloquence and her own prodding using the Force to convince the organization's members to proceed with the plan she had convinced the Twi'lek to propose. Within minutes, the members began planning the capture of Tarsus Valorum, a diplomatic emissary and the Republic's former Supreme Chancellor. The anti-Republic faction intended to strike when the former Supreme Chancellor arrived to appeal to the Counts of Serenno to stop funding organizations critical of the Republic. The following morning, Zannah left the group to their own devices and journeyed to the Sith encampment on Ambria.
Those responsible for executing the plan were tasked with replacing six employees of House Nalju and planting explosives on the landing pad designated for the diplomatic mission by the Great House, one of the most influential families on Serenno. The ARLF chose Kelad'den to lead the five others on the mission, including two senior members—Cyndra, a Chiss female, and Paak, a male Human—along with three other faction members.
The New Dawn landed on a platform extending from a cliff over the ocean, a location that Johun Othone, Valorum's Jedi advisor, disliked. Shortly after descending the ramp, the Jedi felt a strong warning through the Force, a disturbance. He noticed that those ahead, presumed to be members of House Nalju, were armed and that explosives were hidden beneath the platform. However, this warning couldn't save those aboard the New Dawn when the Chiss woman detonated the charges, destroying the ship and much of the platform. As the walkway twisted and began to collapse, Valorum was thrown off the edge. Othone saved him by catching his cape while simultaneously deflecting blaster fire with his lightsaber.
Othone's three attackers abandoned their blasters for vibroswords and charged, aiming for his neck and stomach. Trying to reduce their numbers, the Jedi pushed the female attacker into another opponent and faced the remaining one. Othone then attacked aggressively, killing his adversary. The woman and the other man regained their footing, and the female charged. Instead of parrying, the Jedi dodged her attack, grabbed her wrist, pulled her down onto him, placed his feet on her stomach, and hurled her off the platform. Seeing that he faced a superior foe alone, the remaining assailant fled. As he ran past Kelad'den, the Twi'lek slashed his throat with one of his crescent-shaped weapons, preventing his escape. However, Cyndra and Paak managed to escape without being stopped as they were too far away.
The Twi'lek challenged him, and Othone, wanting to end the battle, charged forward to impale his enemy with his lightsaber. Kelad'den dodged and slashed the former Chancellor's bodyguard's right arm. Adjusting to his enemy's skill, the Jedi attempted to force the Twi'lek back, knowing his weapons were less effective at range. Frustrated by his inability to land a blow, Othone overextended and fell prey to Kelad'den's blades. The Jedi was hit twice, once in the face and once on his left side, then head-butted the Twi'lek, breaking his nose.
After Kelad'den landed several blows and pushed him to the platform's edge, Othone realized he couldn't win, no matter how hard he fought. He chose to sacrifice himself for Valorum, remembering the Jedi adage, "There is no death; there is only the Force." Dropping his weapon, the Jedi Knight lunged for his enemy and grabbed the Twi'lek's shirt. He then leaned back over the edge and fell towards the water. The fall broke Kelad'den's neck, but Othone survived due to the Force. Somehow, the Jedi found the strength to climb the fifty meters back to the landing pad, where Valorum helped him up.
The attempt to abduct Valorum sparked outrage, leading the Counts of Serenno to pledge to eliminate separatist movements. It also led Valorum, in gratitude, to petition the Galactic Senate to erect a monument for the Jedi slain on Ruusan.
Darth Zannah's involvement in this event resulted in her capture by Cyndra and her delivery to Hetton, the leader of the ARLF.
Drew Karpyshyn wrote and conceived the Duel on Serenno for his 2007 novel Darth Bane: Rule of Two. The event served to further develop the character Johun Othone. The repercussions of Zannah's involvement led to the Duel on Ambria.