From Andre Norton’s bizarre D&D novel, Quag Keep:
“We light no more fires. That feeds them,” the cleric continued. “They must have a measure of light to manifest themselves. We must deny them that.”
“Who are ‘they’?” growled Naile. He, too, slewed around to look without.
“The shadows,” returned Deav Dyne promptly. “Only they are more than shadows, though even my prayers for enlightenment and my scrying cannot tell me what manner of manifestation they really are. If there is no light they are hardly to be seen and, I believe, so weak they cannot work any harm. They came yesterday after Ingrge had ridden forward. But they are no elven work, nor have I any knowledge of such beings. Now they gather with the dark-and wait.”
This is a great D&D monster, perhaps more interesting than the classic D&D Shadow. It works especially well in 5e, which does distinguish between darkness, light, and the “shadowy illumination” in which these monsters thrive.
I’d say that these monsters can move around, but not attack, in the darkness beyond the PCs’ torchlight; can attack from shadows; and are helpless and possibly even damaged when inside an area of bright light.
“Is it not true that a spell once used, unless it can be fed from another source, will not answer again?”
This is another bizarre feature of the Quag Keep version of D&D. Each character can use each spell once. It actually seems more like Mazes and Monsters than D&D in some ways – or perhaps Arneson’s original magic system.
While we’re on the magic system…
They backed Deav Dyne who swung his beads still as he might a whip advancing on the black druid who cowered, dodged, and tried to escape, yet seemingly could not really flee. The prayer beads might be part of a net to engulf him, as well as a scourge to keep him from calling on his own dark powers. For to do that, any worker of magic needed quiet and a matter of time to summon aides from another plane, and Carivols was allowed neither.
In this version of D&D, does “any worker of magic” need quiet and time to cast any spell? If so, can spells not be cast in combat? Or is this stricture only placed on summoning spells? (Maybe the latter. In the Greyhawk supplement, the “monster summoning” spells do specify that they come with a “delay: one turn.”)