Light
As Heroes explore the world, they might face pitch-black caverns, dimly-lit dungeons, or the blindingly-bright sky of another world. They may also use spells, tools, or good old fire to light their way.
Total Darkness suggests that there is no light whatsoever to see by. Heroes in Total Darkness are Blind, making combat and navigation exceptionally difficult. Caves and dungeons with no light-sources, as well as moonless nights, are oft in Total Darkness.
Dim Light provides enough illumination to navigate and fight without issue, but not enough to read by. Some dungeons are bathed in dim light, thanks to thin cracks in the stones or the occasional glowing moss. A moonlit night, a candlelit sanctum, a gently glowing artefact, or a simple campfire all provide Dim Light.
Fair Light is bright enough to get things done, without squinting or shielding one’s eyes. Well-lit taverns, a daytime stroll, or the crackling glow of a Torch are all Fair Light.
Bright Light is too bright to see by; details are washed out, and you have to squint to focus on things. While in Bright Light, most Heroes are Dazzled. Staring directly into the sun or at a flash of lightning are examples of Bright Light, as are spotlights, flashbangs, or other forms of focused, concentrated light.
Of course, light sources can be combined to further increase their brightness. Just two sources of Dim Light working together will make the light Fair, but it takes four sources of overlapping Fair Light make a Bright Light.