You’re getting closer, but a bit complex. How about this:
Aura of Darkness (Ex): A live nogra continually secretes a substance from its body that absorbs all visible light in the immediate area, continually surrounding the creature with a darkness effect (as the deeper darkness spell).
Any light effect or similar effect brought into the area of the nogra is suppressed until brought outside of the aura of darkness. Once brought outside the aura of darkness, the light effect resumes. While this darkness will suppress a daylight spell, a daylight spell does not suppress the nogra’s aura.
When the nogra dies, the light-absorbing secretion stops, and the aura of darkness fades away in 1d3 rounds.
Light Sensitivity (Ex): Nogras are susceptible to light sources within the range of their blindsight/blindsense ability. Nogras suffer a -4 penalty to attack rolls when exposed to bright sunlight or a daylight spell. When exposed to a light spell or equivalent light, this penalty is only -2. (I might make this next part into combat flavor text) - When first brought into contact with a light effect, the nogra must make a DC 15 Will save (for light equivalent to a light spell) or a DC 19 Will save (for sunlight or light the equivalent of a daylight spell) or flee from the light source by the best and fastest means available to them. They flee only until away from the light effect, and suffer no further effects.
If a light or daylight spell is cast upon a nogra, the nogra must roll a (Fort?) saving throw. If the save is successful, the spell will simply dissipate. If the save is not successful, the spell is absorbed by the aura of darkness, but the nogra suffers 1d4 points of damage from a light spell, or 2d4 points of damage from a daylight spell.
Feel free to reword that to make more sense, but I think this is how it should go.
