The Dungeon Dimensions not following through their attack on Esk:
Eskarina Smith, armed with a Wizard's staff and the channel of raw magic it represents, is goaded into using it by the Dungeon Dimension things. In a fit of rage, she thinks she is attacking the locked gates of Unseen University. A completely blameless mountainside is blasted into shattered ruin and lava by her anger and the power of the magic she can direct via the staff. The Things, which were using what Esk and Granny later thought was just a hot dream, make no move at this point to enter the world, even though Esk expended a massive amount of magic. But a little later, they abduct Simon into their world. Is it possible that their manipulation of Esk gave them the strength they needed to make a more telling attack on the Discworld - via the intellect and the magical potential of Simon? After all, following through by breaking Esk to their will means they've got a single magic-user with little training or in-depth knowledge. but exploiting her magical potential, so as to be able to break through the university's magical defences and abduct Simon - they have then got a mind which is the gateway to whole worlds. To get to him, they needed power. Esk provided that.
