demiurge1138
Inventor of Super-Toast
I'm okay with an incorporeal fireball.
Death urge seems like a good idea, and Cleon's write-up is fine.
Edit: An incorporeal fireball might be interesting, but it would be a little strange to have it deal fire damage.
I suppose precedents exist for incorporeal attacks dealing fire damage (such as the effigy), so we could probably go with the incorporeal fireball. It would require much less work for the DM.
So...
Alternate Form (Su): A suicide spirit can shift between its apparition and spectral fireball forms as a standard action. In apparition form, it cannot use its fiery touch or fireball attacks, but it can use its Constitution drain. In the form of a spectral fireball, it can make fiery touch attacks, and use its fireball ability, but it cannot use its Constitution drain attack.
A suicide spirit remains in one form until it chooses to take the other form. A change in form cannot be dispelled, nor does a suicide spirit revert to any particular form when killed. A true seeing spell reveals both forms simultaneously.
Constitution Drain (Su): Living creatures hit by a suicide spirit's incorporeal touch attack while in its apparition form must succeed on a DC 15 Fortitude save or take 1 point of Constitution drain. The save DC is Charisma-based. On each such successful attack, the suicide spirit gains 5 temporary hit points.
Fiery Touch (Ex): A suicide spirit in spectral fireball form deals x points of fire damage with an incorporeal touch attack.
Fireball (Su): As a standard action, a suicide spirit in spectral fireball form can explode in a burst of fire. This functions as a fireball spell cast by a sorcerer of a level equal to the suicide spirt's Hit Dice, but the area is centered on the suicide spirit. The suicide spirit reforms in the same space in spectral apparition form 1d4 rounds later.