So let's say your dnd party or course enters a dungen. It's a empty round room with carvings etched into the wall, and a closed door on tge otherwise of the room. When all players step in the room it seals the door, darkness is conjured as a magic trap.

But the darkness spell is special. Darkvision still doesn't work, but you are able to light a torch. You can use magical fire also, or a light spell but it won't despell the darkness. But after a few seconds the darkness will seem to slowly snuff out the light source if it's not maintained.

In the darkness the etching in the wall glow a soft purple. They show off numerous people with little flames in their hands. And words  that read "To those who do not share the heat of life shall freeze in solitude". So basicly if anyone is in the modified magical darkness, they take whatever amount of cold damage the DM roles from a 1D4. This can be stopped by being in any type of light source.

The way to pass the challenge is to take the light source, and to pass it around to each other. And if this goes uninterrupted for 2min the light source will start to grow alittle in size. After the 2min the light source will double in size and will split apart, attaching little pieces of itself to the players. When this happen the etchings on the wall will stop glowing, and the light source will absorb the magical darkness and  despell. Leaving the party in the empty round room with both doors open.

If something interrupts the party will sharing the light around. The light will be put out and everyone take 2D4 cold damage.