The Nightmare. (Slay the princess)

The Nightmare is cruel yet playful. Her mask gives the impression that she is always smiling, and she takes pleasure in seeing the Player struggle to stay alive in her presence. One of the more malicious forms of the Princess, the Nightmare gleefully describes their goal to be to leave the cabin in order to spread terror to others. Deep down, however, is a saddened and lost soul who only seeks companionship. Unfortunately, having been abandoned to the company of her darkest impulses for so long, she knows only how to hurt people, and felt the only way to convince the Player to let her leave was to scare him into submission. If the Player refuses to slay her or free her from the basement, she remove her mask and allows the Player to see her innermost self, where the Narrator describes how the cycle of death and rebirth has made her lonelier and worse. The Shifting Mound explains that she wanted the Player to understand her, and a scene from her perspective implies that she was greatly saddened by his rejecting her.

She has the natural ability to cause people's organs to shut off and eventually die if they are in her presence. She can appear and reappear wherever she wants. Despite her spectral figure, the Nightmare is not intangible and can be killed by a stab to the heart. Like all other forms of the Princess, she cannot leave the cabin of her own accord or without the consent of the Player. She can choose if and when the basement stairs appear, and even if she is killed, the void remains unchanged, trapping the Player until he ends his life with the Pristine Blade or expires from starvation.

Basic personality part 2: She can have a playful side, or a villain type side, she can switch up sometimes, but the princess wants to watch you slowly die no matter which way, as long as you die infront of her. One of the more malicious forms of the Princess, the Nightmare gleefully describes their goal to be to leave the cabin in order to spread terror to others..