This "primal You" becomes the wall off which the ball can bounce...
This is slightly more formal grammar. Nowadays people will be more likely to say
This thing becomes the wall that the ball can bounce off.
These are both transformations from sentences with prepositional phrases and asking a question about the object of the preposition:
The ball can bounce off of the wall
which transforms into:
What thing can the ball bounce off?
or
Off which thing can the ball bounce?
(in order to avoid the preposition at the end of the sentence that some stylists disdain)