ToME WikiOrvin: Target a mountain square and cause a landslide within a skill- and spell-power dependant radius. The landslide has the following effects: 1) monsters in the radius take damage, 2) empty squares within the radius are covered with debris (also killing trees), 3) squares containing objects are covered with debris, with a chance that the objects are damaged or destroyed.
So, this is an area-effect spell, but it can only be used in the vicinity of certain terrain.
If the landslide behavior is introduced, is might also be interesting to allow the possibility that sound, force, gravity, and water attacks affecting mountain squares cause landslides.
Perhaps, there could also be a new trap, only occuring adjacent to mountain squares, which, when triggered, causes a landslide.