Isn't Melf's Acid Arrow no save no SR? I think then that an attack roll could substitute, but you are going for more of an area spell.
My humble version:
Kol's Forceful Blast
Evocation [force]
Level: Sor/Wiz 7
Components: V, S, M
Casting time: 1 standard action
Range: 0 ft.
Area: 20ft. burst centered on the caster
Duration: Instantaneous
Saving throw: none or reflex half (object, see text)
Spell resistance: No
An explosion of force energy radiates from the caster and deals 1d12 points of damage + 1 point per caster level (max +20) to everything in a 20ft. radius centered on the caster, including the walls and ground that might be in the area. Magic items and creatures protected by a force effect (such as a ring of force shield or a mage armor spell) may attempt a reflex save for half damage, as well as creatures with Improved Evasion. A Wall of Force is unaffected by the spell and protects anything behind it from damage. Note that unattended objects in an affected creature's possession are affected as well. Anything destroyed or killed as a result from the damage is blown to pieces and is pushed out of the affected area.
Material Component: 100 gp worth of diamond dust
[A 13th level mage would deal 1d12 + 13 (approx 20 force damage) to everything around him/her while the same mage could have launched a delayed blast fireball for 13d6 (approx 46 fire damage) at an area of his/her choosing. The fireball always allows for a save and SR, but can be set with a timer and thrown at a distance. Assuming it passes SR but the affected creature saves, thats only 23 (fire) damage, which is easier to nullify than force damage. Hence, I made this spell very limited, but ultimately more powerful than the delayed blast fireball (assuming it hits creatures that don't get to save against it), which is why I gave it a small material component (small for someone of 13th level). I deleted some extraneous text about how it is a vacuum as it doesn't seem to have any in-game effect.]
Technik
My humble version:
Kol's Forceful Blast
Evocation [force]
Level: Sor/Wiz 7
Components: V, S, M
Casting time: 1 standard action
Range: 0 ft.
Area: 20ft. burst centered on the caster
Duration: Instantaneous
Saving throw: none or reflex half (object, see text)
Spell resistance: No
An explosion of force energy radiates from the caster and deals 1d12 points of damage + 1 point per caster level (max +20) to everything in a 20ft. radius centered on the caster, including the walls and ground that might be in the area. Magic items and creatures protected by a force effect (such as a ring of force shield or a mage armor spell) may attempt a reflex save for half damage, as well as creatures with Improved Evasion. A Wall of Force is unaffected by the spell and protects anything behind it from damage. Note that unattended objects in an affected creature's possession are affected as well. Anything destroyed or killed as a result from the damage is blown to pieces and is pushed out of the affected area.
Material Component: 100 gp worth of diamond dust
[A 13th level mage would deal 1d12 + 13 (approx 20 force damage) to everything around him/her while the same mage could have launched a delayed blast fireball for 13d6 (approx 46 fire damage) at an area of his/her choosing. The fireball always allows for a save and SR, but can be set with a timer and thrown at a distance. Assuming it passes SR but the affected creature saves, thats only 23 (fire) damage, which is easier to nullify than force damage. Hence, I made this spell very limited, but ultimately more powerful than the delayed blast fireball (assuming it hits creatures that don't get to save against it), which is why I gave it a small material component (small for someone of 13th level). I deleted some extraneous text about how it is a vacuum as it doesn't seem to have any in-game effect.]
Technik
