A similar entry appears in the Wheel of Time Companion confirming the information available in the main story arc.
Author: Kyria d'Oreyn
When Elayne, Birgitte and Aviendha arrive at the Shienaran camp, he comes to meet and escort them to the tent where the rulers of the Borderlands await (WH, Ch. 27). During the Last Battle, he loses two cavalry squadrons due to bad decisions Agelmar makes under Hessalam's Compulsion and is presumably killed himself (AMoL, Ch. 18)
"King Easar sends his assurance of your safety, Elayne Sedai, and I add my own. I am Kayen Yokata, Lord of Fal Eisen, and may Peace abandon me and the Blight consume my soul if harm befalls you or anyone with you in our camp." (Yokata to Elayne upon her arrival; Winter's Heart, Chapter 27)