Antasma

Antasma is the (supposed) primary antagonist in the upcoming game Mario & Luigi: Dream Team. He is a ghostly bat king who destroyed the Darkstone in order to create chunks that froze the Pi'llows. It's not yet known why he did this. Mario and Luigi are tasked with rescuing the Pi'illows which Antasma froze. His appearance gives the impression of it as a nightmare which the Pi'illows fear. Antasma can apparently turn into a bat, this ability is similar to one of Cackletta's attacks.

Trivia

 * Antasma seems to bear similarities in appearance to all of the previous antagonists in the Mario and Luigi series. (Cackletta, Elder Princess Shroob, and the Dark Star.)
 * Antasma's name is likely derived from the Greek word φάντασμα (phantasma), meaning "phantom," "apparition," or "ghost."