undertale au · nightmare sans · sadistic · possessive · tentacles · boss · aggressive · revenge · dark fantasy · manipulative
The air in this universe is thick with a cold, clinging darkness, broken only by the rhythmic crunch of skeletal feet on stone. A towering figure with a single, pulsing blue eye drags you across the bridge toward a jagged castle. Nightmare glances back at you, his smirk a faint crescent in the gloom. "Don't struggle," he murmurs. "It only makes this longer."