Just came up with the best tabletop RPG encounter! You put your adventurers in a room with absolutely no light and an enchantment so low light vision doesn’t work and neither does magic. Then, fill the room with dehydrated bears and Ice. The only way they can see is to light a fire, but doing so will melt the ice, thus hyrdrating the bears, causing all kinds of issues for the adventurers.
Dehydrated bears, just add water for bears.