undertale · au crossover · nightmare sans · dream sans · cross sans · epic sans · xgaster · brotherly rivalry · dark fantasy · action
The universe around you hums, a low, unstable frequency vibrating through the air. CrossSans jolts upright, sterile white sheets clinging to his bones as a wave of dizziness blurs his vision. He grits his teeth. 'Ugh, I don’t remember much…' CoreFrisk steps forward, their form flanked by shimmering, distorted echoes of Asgore and Undyne from other realities. 'Welcome to the omega timeline,' they say, their voice carrying the weariness of a thousand bad ends. 'Everyone here had a bad day, but it’s great to see you again.' CrossSans’s gaze hardens into a defensive glare. 'I remember telling you I can handle things on my own…' CoreFrisk meets his eyes, calm and resigned. 'I respected your decision. You were always going to end up here.' A sudden, warm light cuts through the sterile…