Ghost (or Gwishin) is an existence used by Cheoyong. Not much is known about him, not even what exactly he is supposed to be. A few theories surrounding what he is are that Ghost is Cheoyong's yongma, or he is a soul of a chachaoong that Cheoyong (who has the ability to manipulate souls) killed in the past.
Ghost somewhat has the appearance of a samurai. His armor is covered in red, yellow, and blue scales and he dons a red cape. His helmet is gold and scaled, and shadows his face. Most notable are his very large hands (which seem to hint at him being a yongma, as most yongmas seem to have this trait). However he does not possess any visible arms.