Kossex was a Weequay Jedi of the Old Republic who became one with the Force shortly after the outbreak of the Clone Wars. When the Jedi learned the Separatists intended to attack the cloning facility on Kamino, Kossex was one of the Jedi recalled to participate in its defense. A rare occasion of knowing when and where the enemy would strike, the Jedi intended to lay a trap for the enemy forces.
A impressive collection of legendary Jedi Masters was assembled plan the defense. Jedi Master Obi-Wan Kenobi was chosen to lead the mission because of his familiarity with Kamino. Jedi Master and Council member Oppo Rancisis was chosen as the strategist as he was one of the Jedi Order's best. Jedi Master Tsui Choi was chosen with Jedi Aayla Secura to lead the fighter squadrons that were to intercept enemy fighters. Kossex was chosen to be a part of Red Squadron which was led by Aayla and were tasked with intercepting enemy fighters before they could start their attack runs.
As the Separtists made the jump into the system and the transports and fighters began to descend from the sky above the stormy seas, the defense of Kamino began. As planned, Red Squadron moved ahead to intercept enemy fighters. As the battle began, Kossex warned Jedi Knight Anakin Skywalker of an enemy fighter on his tail and swooped in to intercept. Blowing the droid fighter out of the sky, Kossex saved Skywalker at the expense of acquiring his own fighter on his tail. Aayla Secura made an attempt to save Kossex as he had saved Skywalker, but she just could not get there in time. Kossex's ship was hit and blown into a fireball. Kossex had become one with the Force and joined his many brethren whose lives had already been claimed by the Clone Wars.