The Khazard commander can be found in the Battlefield of Khazard (located south of West Ardougne). He is fought in the Tree Gnome Village quest. To be able to get to him, you must have fired the ballista during the Tree Gnome Village quest. By firing the ballista, it will break the stronghold allowing the player to climb over the wall to attack him. You can not attack him outside of the stronghold even with ranged or magic.