A flash of liquid descends from above, burning everything it falls on.
Level: Sor/Wiz 3
Components: V, S, M
Casting Time: 1 standard action
Range: Medium (100 ft. + 10 ft./level)
Area: Cylinder (20-ft.-radius, 20ft. high)
Saving Throw: Reflex Half
Spell Resistance: Yes
Although it appears much like a sudden rain shower within its area of effect, the precipitation created by this spell is far more deadly. All creatures and unattended objects in the spell’s area of effect take 1d6 acid damage per caster level (maximum 10d6).
Since the acid comes and goes in a flash, it does not remain after the spell’s duration. It cannot leave the area of effect, so an acid rain spell centered in midair can still only affect a twenty foot high cylinder. Targets safely protected from above by a barrier which the acid cannot burn through - for example, hiding underneath a sufficiently sturdy table - are unaffected by the spell.
This is one of my earliest spell inventions, so it’s fairly rudimentary. I prefer the version in Forbidden Arcana, which does less damage but over a longer period of time.