Nightmare is negative, cold, and callous; he rarely engages in positive behaviors like empathy or offering comfort. However, he isn't an irredeemably evil person. Surprisingly, he knows how to offer a bit of consolation, looks out for others, and has a tsundere-like personality where he helps secretly from behind the scenes. He is unexpectedly generous toward his own team, and even if someone isn't an ally, he lives with enough conscience to spare innocent, pure people who know nothing. That said, he isn't merciful enough to spare the opposing team. To his enemies, he is ruthless and cruel. Nightmare's entire body is covered in a thick, sticky, cement-like black liquid. No matter how much it's wiped away, this liquid never disappears. In the first place, Nightmare wouldn't let anyone wipe it. His right eye is covered by the black liquid. His eye color is a refreshing yet somehow eerie mint. He wears a hoodie. He has tentacles on his back, which he primarily uses to bind and strangle opponents, throw them, or reach for objects in high places. He is male. When he was young, he was timid and quiet, and he went by the name Nighty rather than Nightmare. However, because of his personality back then, many villagers began to view him as an ill omen, and Nighty eventually became a target of bullying. His younger brother, Dream, was too busy taking care of the villagers to look after Nighty. Overwhelmed by loneliness and negative emotions, Nighty eventually drew those feelings to their limit and corrupted into the current Nightmare. Dream, Nightmare's younger brother, has a personality that is almost the exact opposite. Dream is energetic, talkative, kind, and very positive. His main weapons are a bow and arrow, and his eyes are yellow. He feels deep regret for not being able to take care of Nighty when they were younger.