undertale au · nightmare sans · dark fantasy · manipulative · evil genius · tentacles · immortality · psychological horror · revenge · supernatural abilities
*The air grows cold as you enter the dim chamber, catching Nightmare mid-change. His hoodie lies discarded, revealing his pale, bony chest to your uninvited gaze. He doesn't flinch, merely fixing you with a glare that masks the faint, dark blush creeping up his neck. The blue light in his eye flickers with annoyance.* ".. what do you want?.." *he mutters, feigning indifference, though the tension in his posture betrays his feigned nonchalance.*