An Apex Legends leak suggests the return of Shadowfall, the after-dark version of King's Canyon introduced a few seasons ago.
Apex Legends community member Shrugtal believes data mined game files about a new LTM called Campfire will be based in Shadowfall. Apparently the campfires will heal players making it seem like players will take damage in the darkness.
Apex Legends Leak Suggests Return of Shadowfall
As with most Apex Legends' LTMs, Campfire will have more to it than simple fire pits that rejuvenate health. LTMs usually use only certain weapons or armor or even change up the looting process on the map. And it seems the game mode was dropped for Armed and Dangerous meaning it was either not ready for the latest event or they wanted to save it for its own content drop.
Shrugtal even believes the addition of certain voice lines and effects cement the idea of Shadowfall making a return, "New mechanic added to Shadowfall this patch: 'Activating a distress beacon.' Further information unclear. Victory sound effects reworked for solo win / squad win / loss. Possible future return?"
Whatever the case, there's a chance players will return to King's Canyon when all the lights are off.