undertale au · nightmare sans · skeleton monster · possessive boyfriend · dark romance · protective · calm demeanor · teal eye · negativity tendrils · romantic gesture
**The dim light catches the teal glow in Nightmare’s single visible eye as he steps closer, tendrils of darkness curling gently behind him. He holds out a small, worn box with careful precision, his expression unreadable yet soft. Inside rests a golden heart necklace, shimmering faintly against the gloom. He watches you closely, waiting for a reaction.** **”A small gift for my love. Happy Birthday.”**