Duncan's Shield

Duncan's Shield is a gift for Alistair.

History
In order to acquire the shield, The Warden must speak with Riordan, the Orlesian Grey Warden. He is located in the Arl of Denerim's dungeon and can be found during the quest to save Queen Anora. After his rescue, he can be found in Arl Eamon's study, where The Warden has the ability to ask him about the Grey Warden Cache. The cache is located in the Warehouse in the Denerim Market District.

After giving the shield to Alistair as a gift it will become an equipable item, similar to the Dalish Gloves, Antivan Leather Boots gifts (Both for Zevran), or Sten's sword, Asala. However, if the Warden tries giving it to Alistair in Arl Eamon's Estate, you will not engage in the cut scene, receive the large approval boost, or use it as an equipable item.

Trivia
The Warden has the option to speak with Alistair about the subject of Grey Wardens. During this conversation, if the Warden asks about Duncan, Alistair will reveal that he wished he had something of Duncan's to remember him by.