The Mask of the Beast is the main antagonist of The Grim Adventures of Billy & Mandy episode "Sickly Sweet". It is a sentient and terrible cursed object made by the Beast and kept by the Grim Reaper's robe.


The wearer's appearance gains purple skin, a reptilian tail, donkey ears, buck teeth and horseshoes.


The mask was made someone from the Underworld called The Beast. Whoever puts it on must be nice, kind, friendly and happy. Or they will turn into a terrible, hideous, beast. Grim owns the mask and Billy decides to let Mandy wear it. Since Mandy is using her meanness, it made her become an incarnation of the Beast even if she struggles to get the mask off her face.


If the wearer of the mask is cruel, the wearer gains fire breath.

Quotes (While Taking Over Mandy)

  • "Mother, I demand bacon, three slices, crispy, trim the fat. One cup of coffee, black. Omelet, three cheese."
  • "Billy, cut it out before I yank your tongue out through your nose."
  • "What mask?"
  • "Billy, what have you done?"
  • "I'll insult you whenever I want to, you blithering nincompoop! Now tell me what's up with this mask before I crush your skull like an acorn!"
  • "I don't believe this!"
  • "Get this mask off my face and be quick about it! Or so help me, it's bone meal for dinner! What's going on here!?"
  • "FRIENDLY!? You dirty..."
  • "Fetch!"
  • "Stop, you stupid dog!"
  • "Stop! STOP, DARN IT!"
  • "Well, I'm listening."
  • "I'LL KILL YOU!!!"
  • "Fine."
  • "Now, if we can just do something about the eyes."
  • "Well, a girl's got to have her principles."


  • Grey DeLisle also voiced a possessor object known as the Exo-Skin from My Life As A Teenage Robot.