They can be ignored in Nights 1, 2 and 3, but from Night 4 onward, they too, pose a threat. When too close to the player, the dark skeleton will hit them with fire. Receiving 2 hits results in death.
Pictures warning: The exposure (brightness) was increased after the screenshots were taken, to better reveal the characters. It was done for the wiki only. The player is NOT supposed to be able to see this well when playing the game.
Behavior EditIn Nights 4 and 5, they can only be found in corridors and in Nights 6 and 7, only in rooms and dead ends. When approached by the player, one of them will awaken and will start following them, with the intention to burn the player. It is possible to lose the skeleton. Once this happens, the skeleton will stay in that spot and will chase the player again if it spots them. Dark Skeletons never disappear, they are constantly inside the dungeon. Also, only one dark skeleton can awaken at a time and pose a threat in the main game. Sparking the light in front of it will temporarily stun it (blind it), buying some time for the player to escape. Sparking 3 times in front of it will defeat it, but not immediately. There seems to be a cooldown between the previous and the next spark, for it to affect the Dark Skeleton.
In the Challenge Chamber Edit
Dark Skeletons are the main enemies in the Challenge Chamber. As time passes and skulls are collected, more and more Dark Skeletons awaken and start chasing the player. Different colors is a sign of their difficulty. As time passes, Dark Skeletons change colors, move faster and deal more damage. After the player collects 5 skulls or more, all Dark Skeletons will be able to kill the player with only one hit. Some screenshots of them are shown in the pictures on the right.
Unlike in the main game, in the Challenge Chamber, sparking in front of a Dark Skeleton will instantly defeat it, except for the overpowered Dark Skeletons appearing right after the player collects the 10th, 20th, 30th,..., 10*N th skull. However, this is only true for the Challenge Chamber, not in the main game. As mentioned above, in the main game 3 sparks with a little time between them are required to defeat it.
Backstory theory Edit
The way they work leads to a theory, according to which, the “Explorer with Unknown Motives” from the original Dungeon Nightmares (the one who wrote the backstory notes) ended up haunting the Dark Skeletons after his death. He killed Mary with fire, exactly what Dark Skeletons do.