A soft round light with Blend Mode set to Add with Invert enabled, which removes brightness from underlying content. Use it to darken areas of the HDRI map.
Please note... you can often get better more controllable results switching to Amplify blend mode, with Invert on.
Here are the key settings for a Dark Light:
Mapping: 3D
Width: 20
Height: 20
Blend Mode: Add, Invert option on, Preserve Alpha on, Blend Channel set to Value.
Content: Bulb
Setting for this light were changed in 9 Drop 4.
The Dark Light now has smarter default settings that prevent unwanted side effects. It no longer affects alpha channels or color, so it works purely as intended - darkening areas without introducing artifacts.
