How do you do the fourth summoning in Dragon Age Origins?

Answer 1

To perform the final summoning, you have to perform all the actions, in order, that you performed during the first, second and third summoning - apart from the last step from each as the summoning symbol won't appear. Then you need to find the summon symbol for the fourth, which is behind a fallen bookcase on the same floor, in the central room with the staircase that leads upwards.