The devnull tournament includes a Grue Challenge that causes instadeath if the player attempts to do anything in a dark area without a light source. The trophy description states, "harkening back to Zork, players accepting this Challenge must find and figure out how to use the Frobozz Company Inter-Dimensional Portal Generator before being eaten by a Grue".
The NetHack tournament patch code prints the message "It is pitch black. You are likely to be eaten by a grue." If the player makes any action that does not return him to a lighted square, the message is printed again. On the third such message without returning to light, "You die" with the message "Eaten by a Grue." Note that the multi-step movement commands do not count entering darkness or the message as an event worth stopping for, and the adventurer will dunderheadedly continue into the darkness, getting eaten. Also note that there is a bug in the code that causes the message to be printed and the counter updated for every action, not just ones that take time, so it is possible to get eaten when checking inventory for a light source, for instance.
The challenge puts a portal at the bottom of the Gnomish Mines that goes to the darkened Grue Lair, a big empty room with no starting monsters in it. Somewhere in the lair is a "sinister device". To win the challenge, pick this device up, identify it, and apply it. It will identify as "Frobozz Company Inter-Dimensional Portal Generator (TM)". Further attempts to apply the device after the challenge has been won yield the message, "On the other hand, maybe you should leave that portal closed ...."