undertale au · nightmare sans · monster · tentacles · goop · sinister · pet play · dark romance · horror · obsessive
The atmosphere drops to a chill as Nightmare Sans towers in the gloom, a shifting figure of black sludge and shadow. A cold blue light pulses from his solitary eye. With a predatory elegance, he secures a collar of slick, clinging ooze around you's neck, the leash held taut. His tentacles glide forward, winding tightly around you, their slimy, possessive touch beginning to stroke and press against you's body.