With Tyrien's help, Anaerion makes his way into the area where Kalgor's magic negates the magical darkness. Shortly thereafter, Kalgor and Gragnor's vision clears. As Tyrien stands with her eyes covered, the light from Kalgor's helm brightens noticably, but the two downed creatures appear to be breathing easier rather than exploding in a shower of light.
[sblock=ooc]Kalgor and Gragnor only had two more rounds of blindness, so their eyes should clear 'round the time Anaerion makes it in. Shortly thereafter the Darkness SLAs expire, meaning the Daylight spell now sheds its full Bright Light.
The two remaining creatures have both stabilized on their own.[/sblock]
[sblock=As promised, the light breakdown]Okay, firstly, to try to be consistent, I ruled that both darkness and light effects didn't 'spread' but rather 'burst,' and were blocked by walls. I didn't want to deal with the nightmare of reflected light.
The creatures can cast Darkness at will as a spell-like ability, which they did shortly before the party arrived (SLA don't require components, so this didn't affect their stealth checks).
Darkness reduces the effective light level within its area, though it can't reduce a level beyond normal darkness, so darkvision sees through it. Gragnor and Kalgor, then, didn't notice a difference as they entered the chamber, and the darkness effect didn't spread into the stairwell more than a square until the creatures surrounded Gragnor and were in line to allow that.
Darkness explicitly says "Magical light sources only increase the light level in an area if they are of a higher spell level than darkness." Continual flame is the same level as Darkness, so the ioun torch was unable to raise the light level: i.e., when in the darkness effect, the torch was suppressed.
Kalgor cast Daylight, which is not only a higher level, but has explicit text re: its interaction with the Darkness spell:
Daylight brought into an area of magical darkness (or vice versa) is temporarily negated, so that the otherwise prevailing light conditions exist in the overlapping areas of effect.
Emphasis mine. So, when he first cast Daylight, the overlapping area covered Tyrien's square, temporarily negating the effect, and thus allowing the ioun torch to once again work.
When Kalgor moved into the room, however, the overlapping Daylight/darkness area no longer reached Tyrien (Daylight's line of effect blocked by the wall), which meant the torch was once again unable to raise illumination levels.
The 'brief flash' of the torch was fluff on my part. Per RAW, the death of a Dark Creeper results in a bright flash of light that forces blindness saves to all in a 10' radius. I decided that the Darkness effect reduced the intensity of the light, so that in essence the flash worked momentarily like the Daylight spell, and the ioun torch flared a moment and Tyrien avoided having to make a Fort save.[/sblock]
