Ice troll runts are not found on the northern isle with the rest of the ice trolls, but they are found in the cave systems (the eastern cave before completion of The Fremennik Isles, and the western cave after). They're also found south of the bridge to the troll isle just north-west of Neitiznot. They are spread out and the Honour Guards tend to attack them. This is an excellent location because it is possible to join in the fight of the Honour Guards. You only have to the hit the trolls once to get the drop, which can be very beneficial as you can make the Honour Guards take all the damage. This tactic can be used effectively with range, magic, or melee as the trolls will always attack the Honour Guard preferentially reducing the damage taken by the player.