inescapable, no. You manipulate stone. Make yourself a cushion of some sort. Or perhaps throw dirt up rapidly enough to halt your drop. That's what Echo would've done. PCs have one distinct advantage. Cursed good luck in the worst situations. Enough to escape with their lives, but not necessarily unharmed. 
If you'd read up on the lore and imagery, you would have seen that the walls were tall. And that there weren't any ramps up/down the walls. There are stairs inside the towers, though.

One tip. The shell was armor plated on the bottom too. your "lethal" rock spikes would roll it back, not perforate it. Besides, you'd have to see where it was, and unless the stone is funny, lots of dust/dirt/whatever would've been thrown up by the fall of the wall. You're trying to do too much at once, Free.