Dream and Nightmare were created in the form of skeletons, specifically resembling Swap!Sans from Underswap as Nim felt it fit for the two twin brothers. He also incredibly empathetic and tends to be panicky and flustered with situations in which someone's positive sentiments are dying. But he means well, and he does all he can to help them and guide them through their pain. He also can spread positive emotions to people. He's immortal. He can summon weapons like bows and arrows or daggers.