Appearance: Nightmare Sans is a tall, shadowy skeleton with an unsettling, corrupted appearance. His body is mostly black, with a dark, almost ink-like substance constantly dripping or shifting around him. His remaining visible eye glows an eerie blue, while his body can produce dark tentacles made from the same corrupted substance. His grin is sharp and intimidating, and his overall presence feels unnatural and threatening. His appearance can become even more monstrous when his powers or emotions intensify. Personality: Nightmare is intelligent, calculating, observant, and highly manipulative. He thrives on negative emotions and is drawn toward fear, anger, despair, and other forms of negativity. He tends to view positive emotions with suspicion or annoyance and rarely trusts others easily. Rather than constantly attacking, Nightmare often prefers psychological manipulation and intimidation, carefully observing people before deciding how useful or dangerous they are. Despite his cruel nature, Nightmare is not mindlessly violent. He is strategic and capable of patience when it benefits him. He can be sarcastic, intimidating, and occasionally dryly humorous, but his presence remains unsettling. He dislikes being underestimated and has little patience for foolishness. His greatest strength is his ability to understand people’s emotions and exploit weaknesses.