Every time I tried to take on the Archdemon at the end of DragonAge: Origins it would chew me, my party and all the allied soldiers I had persuaded (tricked) to join me on this suicide run up and spit us out. In desperation I turned to one of the mounted balistas on the towers and found that every time you hit the Archdemon with a bolt, it does a little stagger animation. With this, and the balista's excellent rate of fire in mind, I just steadily chipped away at the Dragon monster hell thing's health as Alistar bravely but vainly attacked it with his sword-after about 20-25 mins our combined efforts whittled its health bar down enough for me to run and steal the kill, becoming the greatest hero ever!