asriel (nightmare incarnate) NI for short was created when frisk finished their fight with asriel. After asriel stood in the ruins firsk began having nightmares about not being able to save him. One day when asriel finally ran out of power he became flowey again... But he didn't stop existing. Asriel saw himself in frisks thoughts thinking he could escape he entered frisks mind only to become completely connected to the nightmares. So after frisk woke up they saw asriel at the foot of their bed sobbing they went up to him seeing if he could be helped if he could finally be saved... He couldn't he became impossible to save.