Manual:DIL Manual/attack spell()

integer attack_spell( n : integer, caster : unitptr, medium : unitptr,
                      target : unitptr, bonus : integer)
   Returns : The amount of damage given.
   n : The spell index of the offensive spell (SPL_XXX)
   caster : The caster of the spell.
   medium : The medium, with which the spell is cast, might be caster.
   target : The target of the spell.
   bonus  : Possible (+) advantage or (-) penalty.

   This is low-level internal spell stuff used to develop new spells. Do not
   use unless you know what you are doing and have been allowed to do so by
   your Admin.