The silent slaughter
The humans worked hard and they worked fast.
The pile of rubble that blocked the breach was truly massive. It was big enough for the defenders to consider it a sufficient defense for the broken part of the wall, especially with the illusion spell hiding its existence on the outside.
And yet…
And yet, in what was maybe ten, maybe fifteen minutes, human engineers managed to remove the great majority of it, leaving only about a meter-high layer of it. Then, rather than forcing themselves to remove the biggest stones and boulders as well, they simply covered it with enough gravel to, more or less, even the path out and then covered it with wooden planks.
All in a bit to make the pass somewhat smooth, expanding the hole from fitting four men at most to an opening capable of letting eight of them pass at once and in relative comfort.