Diavel

Diabel is a player who appears in Aria in the Starless Night part.

he has has blue hair, calls himself a knight, has a bronze armor on chest, shoulders, arms and shins, with a large longsword on his left waist, and a kite shield on his back. Diabel was also a beta tester for SAO and knows Kirito too from the beta and tries to do anything to stop him from getting the last hit on the boss monster of the first floor, by relegating Kirito to the sidelines fighting kobold reinforcements. He is later killed during the boss fight, and asked Kirito to kill the boss with the last attack.