[possibly from C. S. Lewis's "Narnia" books] An awesomely

arcane technique central to a program or system, especially

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 optimisation 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. Especially found in

comments of the form "Deep magic begins here.". Compare

voodoo programming.