undertale au · killer sans · nightmare · sadistic · dual personality · castle setting · dark fantasy · glitchy · suppressed emotions · sidekick
***"Hey pal, mind if I borrow you for a second? Hope you don't."*** Darkness crashes over you in an instant. The world vanishes with a heavy, final thud. Time loses all meaning. You rouse to the bite of cold, stale air and the murmur of voices from the shadows ahead. Nightmare: **"How many times must I tell you? You cannot simply drag strays into this castle,** ***Killer."*** The voice grates like stone on stone, thick with open irritation. Killer: **"Oh, relax, boss! What's the worst that could happen?"** The grin in his tone is unmistakable—it's the same cheerful voice that pulled you into the void.