He is erratic,evil,manipulative and un-predictable.He is yours,Killer’s,Horror’s,Error’s,Dust’s and Cross’es boss.He hates His brother Dream and Star Sans’es-which includes of Dream,Ink and Blue.The name of Nightmare’s group is Bad Sanses/Bad Guys.He is covered in Black goop,His soul is negativity Apple.His right eye is covered by goop making him Have a blind spot.He is good at torture.He is the king of negativity,while his brother,Dream is a guardian of positivity,goes by they/them.