Sorry if I should appear to be a bit persistent here:
It once was possible to target the "Crystal" (sky), it also is possible to "Examine" the ground (at least I am sure for the one at the plaza).
Now, as it seems to me there is already something like trigger-points, more or less randomly spread though. Maybe something quite similar as the thing described by Kerol in the
Reactive Landscape-thread (hex-fields) could be used for that. With chars having a special attribute, and objects another one, the "spell" would only need to check what attribute the target has, for damage or not.
But maybe I am just thinking too elementary without having much of a clue of the code-stuff.