It took years before I understood.

All my life, we lived on the plateau. High ground was safe, whether it be mountains or hills, we never risked the lower territories, and we never – ever – went into the valley. Even after our monolith fell and the pieces crushed portions of our town, no one ventured to lower elevations for help. The isolation was too much, especially when I entered the valley myself, and met the Sorceress.

Her house was a door in the cliff face, and inside was a labyrinth which could drive any sane person mad if they were too rigid in their perceptions of the world. Why I demanded to be her apprentice, I can only attribute to a misplaced sense of self-preservation, but I learned far more than the tidbits with which she bated my curious mind.
I adopted her craft, made it my own, and slowly began to see how Magic truly works. You see, it flows like water – downward. The higher you are, the less magic there is, and the safer you are from it.

The valley was the lowest area in our awareness.