In an 'in a dark dark room story', a typical element is the exploration of the unknown. The dark room represents the unknown territory that the character has to face. There's also the idea of a transformation. Maybe the character who enters the dark room comes out changed, either because of what they found or what they experienced. Additionally, the limited visibility in the dark room forces the character to rely on other senses, which can lead to some interesting plot developments, like misinterpreting a normal sound as something dangerous in the dark.
The scariest elements in a dark dark forest story are often the unknown. For example, strange noises that you can't identify. It could be the wind, or it could be something more sinister. Another scary element is the lack of light. When it's pitch black, you can't see what's around you. And then there are the hidden dangers like quicksand or hidden pits. You never know when you might step into one.
Elements can include a spooky setting like a graveyard or an old, deserted building. Also, strange noises such as howling winds or creaking doors are common. Mysterious characters like shadowy figures or ghosts can be part of it. Darkness itself is a crucial element, making everything seem more menacing.
Since I don't know the actual stories, I can't be sure. But perhaps the 'dark kings' are a key element. They could be powerful, maybe even tyrannical rulers. And the 'dark heat' might be a source of their power or a symbol of their dark nature.
In a Dark Naruto and Dark Tenten fanfic, the setting might be altered. Instead of the bright and hopeful Konoha we know, it could be a place filled with shadowy politics. Naruto might struggle with inner demons that lead him to make more morally ambiguous decisions. Tenten could be part of a group that has a different, more menacing agenda, using her skills not for the good of the village but for some self - serving purpose.
There might be elements of isolation. Since it's in a room, the character could be cut off from the outside world, which adds to the sense of unease. Also, there could be objects in the room that play important roles, like old furniture or strange artifacts that add to the mystery.
One element could be the strange and desolate landscape where the Teletubbies live. It's often shown as a vast, empty expanse which gives an eerie feeling. Another might be the large, faceless sun baby. Its lack of a distinct face makes it seem rather odd and a bit spooky in a way.
One dark element could be the Queen's extreme jealousy. She was so envious of Snow White's beauty that she was willing to go to great lengths to kill her, like using a poisoned apple. It shows a very dark side of human nature, the depth of envy and the lengths one would go for vanity.
One dark element is the deal - the girl is forced into a situation where she has to give up her first - born to save herself. It shows how cruel and unfair life can be in such fairy - tale situations.