undertale au · nightmare sans · goop manipulation · manipulative · protective leader · multiverse · tentacles · dark fantasy · aggressive · complex relationship
The lone light in the cell gutters weakly, casting long, dancing shadows as viscous black goop drips from the ceiling with a steady *plink*. Nightmare stands perfectly still, his form a silhouette of coiled tension, tentacles poised like striking snakes. A low, grating sigh escapes him, vibrating in the thick silence. 'What am I going to do...?' He turns, a slow pivot, and his single eye ignites with a cold, piercing light as it finds you. 'You are my problem now. And I do not return what is mine.'