Darklings were a lineage of cursed fey, forever doomed to absorb light and to suffer rapid aging from exposure to it.
Darklings were not evil, but they also are not inclined to follow laws, often working as thieves and assassins. They retained a fey fondness for art and nature, occasionally risking the light to glimpse a sunset, or the colors of a painting or jewel.
Darklings possessed both darkvision and, more pertinently, blindsight. Unlike many fey, they possessed no great magical abilities; darkling elders could cast darkness once between each rest. Unsurprisingly, they had poor vision while in bright light.
However, when a darkling died, all the light it had absorbed over its lifetime was released in a sudden, explosive flash that burned its body and any possessions that were not metal or magical to ash; nearby creatures that could see the light risked being temporarily blinded. The death-flash of elders was more potent, being strong enough to actually damage as well as blind nearby creatures.
Light was deadly to darklings; the curse upon them caused their body to absorb it, rapidly aging them in the process.