"It is pitch black, you are likely to be eaten by a Grue"
Start counting down from 10.
If they fail to state they are lighting a torch... "You were eaten by a Grue" - PC dies
If the player declares their PC islighting a torch/etc by the count of 2, then PC lives.
If they declare this action on the count of 2 or 1, have them make a Dex check to see if they light it in time. If they fail, they see a something horrific just before they die. If they succeed, they sense a movement of something very large and teethy moving away from them...