The Night Sword is an incredibly pointy sword with a low purple hue. Its hilt has two seemingly flat eyeballs on opposite faces of the sword and can flip out to reveal a built-in compass. The eyeball color appears to have a dim light-blue glow and is incredibly glossy. The sword is cursed since it was forged by Peppermint Butler and blessed with Nightosphere magic by Hunson Abadeer.
It should be noted that a much bigger version of the sword exists, wielded by a colossal and much older Sweet P. It is never explained if it is the same sword or not, as it was only briefly seen for a few seconds in "Come Along With Me."
Not much is known about the sword. As shown in few episodes, it is powerful enough to defend from the attacks from the Green Knight, having the curse given by Hunson Abadeer, and is also therefore capable of causing harm to ethereal beings such as ghosts (as explained in "Marcy & Hunson.")