The Witcher 2: Assassins of Kings -
"The Dun Banner can be found outside the Old Gate. You'll be ambushed by Nekkers on the way. Beneath the ground you'll be attacked by Wraiths. Use Aarn on the stone walls to meet the undead commander. You can fool him into giving you the banner without a fight. Tell him that you were a Dun warrior. When he describes the formations in battle, tell him he got it worng. When asked who led the troops at Berne, tell him it was Coehoorn. When asked about Coehoorn's future, tell him Coehoorn was dead. When asked who commanded at his last battle, tell him it was Vandergrift and Seitkirk. When asked how you escaped, tell him Biggerhorn took you prisoner. He'll reward you with the Banner and magic sword.