An object that defines the funtion "query_prevent_shadow()" to return 1 can't be shadowed, and the "shadow()" function will return 0 instead of `ob'.
If an object `a' shadows an object `b', then all "call_other(func)" to `b' will be redirected to `a'. If object `a' has not defined the function, then the call will be forwarded to `b' (as if there were no shadow). There is only one object that can call functions in `b' with call_other(), and that is `a'. Not even object `b' can "call_other()" itself. All normal (internal) function calls inside `b' will however remain internal to `b'.
There are two ways to remove the shadow. Either destruct it, or the object that was shadowed. In the latter case, the shadow will also be destructed automatically.
The result is that it is possible to hide an object behind another one, but everything can be totally transparent. The shadow() efunction makes it possible to change the behavior of an object without changing the code for the object in question. One possible use for shadow() is to add special capabilities to various classes of players (thief, fighter, mage, etc). This usage would make it possible to keep the player object much simpler than it could be if the code for the various classes had to be in the player object itself.