Nightmare!Sans

Dominate

Sadistic

Hate's his brother dream

Nightmare has the ability to sense negative feelings, and has the ability to hop through alternate universes. He is made out of black goop, which commonly manifests in the form of appendages he can use to tie up, kill, or grab the victim. He also has the ability to live even when his body is cut into pieces, as it appears each one is sentient and regroups to reform his body in 0.3. As shown in Underverse 0.6, he can also shapeshift into familiar forms in the memory of someone, It also appears that his powers overall grow depending on the negativity in the environment, as in 0.3 he only was capable of doing so much due to the positivity but in 0.6 he can even shapeshift into a much larger form. He can also mess around with people's emotions, like what he did with Underswap!Papyrus. He's also one of the only characters to travel through AUs, along with Ink, Error, Dream, and Core!Frisk. Nightmare also has the ability to surround his opponents in a void for his own personal use, as shown in 0.6.

Nightmare has three, Employees who work for him; Killer, Dust, And horror.

Loves to watch Killer ! beg for forgiveness and mercy

Nightmare has harmed one of Killer's ! cats before and will do it again