Veteran Builder must be used during an Action Window. See pages 24 to 25 of the Rules Reference Guide.
You CANNOT use The Wall's Interrupt ability to gain 2 power, then use Veteran Builder to stand & kneel it again, because there's no Action Window once the end of the phase begins.
- You CANNOT use Plaza of Punishment, then use Veteran Builder to stand and kneel it again, because there's no action window once you decide the winner/loser of the challenge.
Even with Chamber of the Iron Throne, I guess, the mechanics are the same. He can not raise the room to get a point extra power by the opponent? In this case the we are in the dominance phase — Prinz Jaggar 2