[ Essek nods--finally, something within his wheelhouse. ]

The practice and study of Magic is my specialty, and this seems to be a particularly strong enchantment if, as you say, it applies to the entirety of this city. It is, perhaps, bolstered by the work of many mages, as well as a handful of magical items. Without knowing the source I cannot be positive as to the details, but I can make an educated case.