Explain the destruction of Charn

The Queen described the destruction as "great peril". She was calm and led the others firmly away from the crumbling structure. The breaking up of the palace is described as "first a rumbling, then a creaking, then a roar of falling masonry, and the floor shook." As the Queen led them out of the palace, the walls crumbled behind them. The Queen uses magic to break through the last doors on their way out, leaving a heap of dust on the threshhold.