2014-02-09, 02:41 AM
I have never added a completely new spell, but I'm pretty sure what you're describing is doable. I think the "on target" spell is an animated MDL file. So you would make a similar animated model of rock-spears that started below ground and then jabbed up above ground level.
Then you would find the "on target" dragon head entry in the SFX.dat file and copy it's entry to a different 'slot' in the sfx.dat and change the entry to refer to the new rock MDL.
Lastly, you would make a new spell PRF file that pointed to the new spell slot.
None of that is as hard as it probably sounds and I'd be willing to help with the SFX.dat stuff if you'd like to make the animated model of rock spears. 
Then you would find the "on target" dragon head entry in the SFX.dat file and copy it's entry to a different 'slot' in the sfx.dat and change the entry to refer to the new rock MDL.
Lastly, you would make a new spell PRF file that pointed to the new spell slot.
None of that is as hard as it probably sounds and I'd be willing to help with the SFX.dat stuff if you'd like to make the animated model of rock spears.