The problem I have witha bility damage, is that it reduces everythone to 3-18 HP. granted with stat booster one can have a high 20's WIS, but it still elimates one of the main protection mechanisms - HP.
That being said:
This operated as a L1 spell: obscuring mist, a L3 Spell Dispel magic (for light sources only), and a L3/L4 spell: Poison. IN addition you want it to ignore SR (very few spells do), and have a frightening area of effect.
To offset this, you wish to add a matierial component, and have a spell casting time of 1 full round.
I can see this as a 6th level spell. As a cone, with SR, and a fort save. Require a material compenent in which the caster must drink a potions of poison (which would casue an AoO if anyone threatened the caster -> good). Potions of poison are not cheap, or plentiful (only druids can make them).
Also, he duration should be Instantanoues, and 1/round a level. the dispel effect and poison effect can only occur once, regardless of duration. The dispel check for magical light sources is limited to 10, and the poison does 1d8/1d8.
Oh, and make it necromatic
