From Halopedia, the Halo wiki
According to the legend, Nesh 'Radoon was a powerful sea lord and rival kaidon of Kel 'Darsam. Being a slayer of monstrous sea creatures, Kel 'Darsam expressed little interest in becoming kaidon, and so he gladly left the position to his uncle, Orok 'Darsam. During one assault on 'Darsam's familial keep, Kesh 'Radoon captured Orok. In response, Kel invoked the "right of release" and sailed off on his own to liberate his uncle. Under the cover of night, Kel freed Orok after he scaled the sheer walls of 'Radoon's keep and slayed the keep's best swordsmen. As the two made their escape to safety, Kel was mortally wounded when a spear struck him in his back. Before falling to his death, Kel was touched by the rising light of his divine father, Urs, and was transformed into pure light.
Due to two versions of the ballad in existence, modern Sangheili are unsure who threw the spear that struck down the brave hero. In one account of the legend, Nesh 'Radoon is responsible for throwing the spear and killing Kel 'Darsam. 
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