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Kannos is an Etti, former leader of the Genoharadan and former companion that the player's character gains in the conversion mod for the video game Star Wars Knights of the Old Republic II: The Sith Lords: Star Wars Knights of the Old Republic III: The Jedi Masters.
He is a former major protagonist and later the main and final antagonist of the mod.
Leader of his company on the world of Etti IV, Kannos is called to a meeting on Onderon with the Queen Talia, the player's character (known as "the doctor"), the Republic and the armies of HK-51 units led by HK-47 about finding Revan. The meeting becomes sour, with everyone ending up fighting each other, with the doctor and his assistant, Tsig, escaping the madness and persuading Kannos to help them escape by letting them ride in his shuttle with him. However, they crash land on the nearby moon of Dxun, so they find the tomb of the ancient Dark Lord, Freedon Nadd. After the doctor explores the tomb and becomes tainted by Nadd's spirit and trained by him in order to become a Jedi and retrives a lightsaber in the process.
After that, the doctor and Tsig ruins of the Mandalorian camp and some Jawas with scientific abilities and with the help of their leaders, Borran, Canderous Ordo (Mandalore) and Ootataa (a shape shifter), they manage to repair another damaged vessel called The Eagle and leave the planet with Kannos incaged by the famous assasin known as the Shadow who states that Kannos cannot be trusted. The doctor talks to Kannos and he agrees to help him find Revan in order for his release. The doctor and his companions scour the galaxy, gathering Bastila Shan on Telos IV, T3-M4 and HK-47 on M4-78B and Meetra Surik (The Jedi Exile) on Etti IV. After the doctor returns Kannos to his position that had been stolen from him as head of the Genoharadan on Etti IV, Kannos gave the doctor his reward: the coordinates for the Aperture Station.
There, they find Kreia (who was brought back to life and kept alive by scientists after the events of the previous game). Kreia agrees to help them find Revan and she too joins the party. With the persuasion of both Bastila and Kreia, T3 gives the doctor the coordinates for Revan's last known location and they head to an apocalyptic-looking planet of an unknown name. The doctor, Bastila and Kreia head out to an ancient tomb after battling their way through Rakghouls.
However, the True Sith, find the Eagle in space and capture the crew and imprison them all. Their leader, D'arth D'narth (a Sith Lord of pure darkness, and now a thousand years old) arrives and spies Kannos. He seduces him and corrupts Kannos into becoming his master and allows Kannos to embrace the power of the D'arth Syyth and becomes the new leader of the True Sith. Kannos confronts the surprised doctor who arrives with Revan and Bastila while Kreia stayed behind on the Eagle, and they fight. The doctor proves more than a match for him and D'narth takes him away from the battle, leaving Sunrider (a former follower of his) to get captured by the crew, who escape with Revan, Bastila and the doctor.
After they escape, Kannos D'arth Syyth intends to put his plans of using the power of the D'arth Syyth to destroy the galaxy. They first attack the rebuilt world of Taris and Kannos unleases the plagues of the Rakghouls, Banshees and Screamers (the followers of the True Sith) upon the men, woman and even children of Taris before destroying the planet with the power of the D'arth Syyth. Kannos eventually became so mad with the power he was given that he destroyed D'arth D'narth and teamed up with the resurrected Darth Nihilus, who intended to use his power of destruction upon the universe as well.
After Nihilus and his forces were defeated on Rhen Var by the doctor, Revan and the united Jedi Masters throughtout the galaxy, Kannos D'arth Syyth launched a massive attack on Coruscant and headed down to the Republic Senate and killed Supreme Chancellor Cressa before leaving the rest of the senators to D'arth Kilmore, who was later killed by the Jedi Exile, Meetra Surik during the battle. Revan, the doctor and their companions fended off the screamers, banshees and rakghouls and split up.
Revan, the doctor and Bastila boarded the Nemesis vessel to find Kannos and the D'arth Syyth and to stop them while Canderous and HK-47 activated the other HK units to help them in their battle against the Sith, Ootataa fended off a Storm Beast, the exile killed the invading Sith in the Senate and Bastila killed D'arth Scarr (another follower of the D'arth Syyth. Revan faced Kannos alone with a plan (to give into the Dark Side in order to kill Kannos so that he may become the new D'arth Syyth and use the D'arth Syyth to destroy itself along with the entire Sith fleet).
Kannos and Revan entered an epic battle to the death. With Revan winning the first two rounds, Kannos declared the third and final round before losing to Revan again. But before Revan struck down Kannos, his last words were spoke "can't the villain win just once?" Revan then enacted his plan and finally the True Sith were no more and the D'arth Syyth was destroyed along with Revan and the entire fleet in the process, ending the war and stopping the destruction of the galaxy.
In the 2.0, there are many alternate endings to Kannos' story and therefore, to the end of the game.
In one version, the doctor lets Revan kills Kreia and therefore either let him kill Kannos and sacrifice himself to destroy the Syyth and save the galaxy or interrupt Revan during the duel and allow Kannos the chance to kill Revan in a Dark Side ending and then the doctor would fight Kannos and kill him for the power of the Syyth and take the power for his own to use.
Or the doctor would kill Kreia himself and go on to fight Kannos himself and defeat him and sacrifice himself to save the galaxy.
Or the doctor would stop Revan from killing Kreia and when Revan fought Kannos, Kannos would instead win and destroy Coruscant and remain as the Kannos D'arth Syyth.
Or in the ultimate Light Side ending, Kannos had fallen in love earlier during the game with a female Twilek named Nizzal. He told the doctor this during a conversation and they found her on Etti IV with a husband and Kannos didn't think that killing another one of her husbands to win her over was worth it. After the doctor allows Revan to go fight Kannos but stops him from killing Kreia in the process. When the doctor's Jedi apprentices come aboard to help prepare the escape pods for him and Bastila, the doctor will go and help Revan in his duel with Kannos and remind Kannos of Nizzal, telling him that if he destroys the galaxy, he will destroy her too. Eventually Kannos comes through and lets Revan and the doctor escape the ship with Bastila and the doctor's apprentices as he sacrifices himself to destroy the D'arth Syyth and it's fleet and save the galaxy in a final act of redemption.