Marcus Gaw

Marcus Gaw is the third and last Darkwalker leader that needs to be defeated to acquire the code to release the force field to complete the "Rescue of Karl Eckener". He can be found in the same cave system as Karl at coordinates -4030 -248 4297 by returning to the first junction just inside the entrance and with your back to the entrance taking the left turn or from Critolus Masse by setting off back towards the entrance and at the first junction that you then reach taking the turn to the left.