Well in my headcanon my Aeducan was there, along with Loghain (and maybe some other characters. I dunno). But I suppose it would go something like this.
Fear Demon: Xanthos Aeducan, King of Orzammar, Hero of Ferelden, Vanquisher of the Blight, and Paragon to not just the Dwarves but to all of Thedas. Do you truly believe you can save your people from extinction? Do you truly believe you can undo centuries of damage? How arrogant of you. All you have done is prolong the inevitable. How many people died because you were too afraid to kill Bhelen, because he was family? How many Dwarves died because of your weakness, their blood paving the way for your throne of lies? And you cling to that spirit of yours -- and indeed, that Spirit -- so tightly. Does death frighten you so? Is that not why you agreed to your beloved Morrigan's offer, so you wouldn't die against Urthemiel? Your mind will rot away, as it does for all Wardens. You cannot escape your fate, Your Majesty. Death will come no matter what, for you and for all those you hold most dear. Your wife in Orzammar and Morrigan and Leliana, your son Kieran, your family and friends. You will lose it all."
Xanthos: Do your worst Demon. Nothing you say can change where I stand or who I am. I have killed many of your kind and I'll not fall to false words you utter to compensate for your own weakness, nor idle threats that I've heard time and time again. I am here, I will remain, and you are but a fleeting shadow in the trail I walk. "
EDIT: Actually I kinda imagine it would continue past Xanthos' comeback, with the two of them just going at it for a bit with their own retorts.