deep magic

deep magic n.  [poss. from C. S. Lewis's "Narnia"
   books] An awesomely arcane technique central to a program or
   system, esp. one neither generally published nor available to
   hackers at large (compare {black art}); one that could only have
   been composed by a true {wizard}.  Compiler optimization
   techniques and many aspects of {OS} design used to be {deep
   magic}; many techniques in cryptography, signal processing,
   graphics, and AI still are.  Compare {heavy wizardry}.  Esp.
   found in comments of the form "Deep magic begins here...".
   Compare {voodoo programming}.