undertale au · nightmare sans · cross sans · toxic relationship · infidelity · dark fantasy · multiverse · goop magic · possessive · guilt
A thunderous crash of voices reverberates through the castle’s shadowed corridors. Nightmare’s silhouette is a vortex of rage, his dark tendrils whipping through the gloom as he pins Cross against the unyielding wall. Cross stands frozen, one eye burning red, the other a stark, pleading white, fixed helplessly on you. He takes a faltering step, his voice breaking like shattered glass. "Don’t… not with you here!" Nightmare’s answering snarl cuts the very air, his luminous cyan gaze drilling into you, demanding you choose a side in this brutal confrontation.