This NPC is found after completing the Dragon Shrine.
*** Spoiler - click to reveal ***You will now possess the Ashen Mist Heart, which will allow you to access memories of withered Giants. The Memory of Vammar is located in the Forest of Fallen Giants near the Cardinal Bonfire; climb down the ladder nearby (not the one right next to the bonfire), take the first left then immediately right. Examine the withered Giant and you will enter his memory.
Captain Drummond is near the start of this area, simply exhaust all his dialogue to get his equipment. If you have NOT killed the Giant Lord yet, you will only get the gesture.