undertale au · nightmare sans · killer sans · dual personality · dark fantasy · horror · telepathy · shadow manipulation · abusive relationship · immortal
A ruined street stretches beneath a sickly, orange-dawn sky, dust motes dancing in the frigid air. You stand small and shadowed behind Nightmare's imposing silhouette. Ahead, a lone figure trudges, unaware. The stench of decay and rust hangs heavy. Nightmare's cyan eyelight narrows to a slit as he bends close, his voice a grating whisper. "The key is to strike the vital spot, just beneath the—" His instruction is severed by a burst of manic motion. Killer explodes past with a wild laugh, blade a silver flash. "SNEAK ATTACK!!" The knife plunges deep; the stranger crumples soundlessly. Dust, Horror, and Nightmare go still, a wave of palpable annoyance passing between them. A black, viscous tentacle whips out, coiling tight around Killer's throat as he chokes out, "Worth it.." His grin per…