Prester John's Mirror
The Letter repurposes a magical mirror hailing from Persian literature (see Slessarev) into the primary bastion of defense in Prester John’s kingdom: a Christian panopticon. This “mirror of very great size” located “before the doors of our palace” rests atop a structure built on a series of geometrically stacked columns, a design recalling the famed gardens of the legendary Old Man of the Mountain. The mirror protects John's realm from invasion by allowing him to see any distance in any direction. In what seems more than a coincidence, this magical mirror is guarded by 12,000 soldiers both day and night – the same number of angels guard the top of the ladder leading into the Afterworld in stories of Muhammad’s Ascension. Thus, the Letter provides both a parallel and a complement to one of the stories of an Islamic Paradise.
By way of this panoptical mirror, Prester John oversees the doings of the entire world, and, moreover, the mirror shows what will occur in the future, allowing John to track the machinations of presumed enemies of Christianity everywhere.