Gray Guardian (그레이 가디언, geulei gadieon) is a guardian on the Hell Express that was most recently was seen as the opponent of the 38F stage test of the train. The "guardians" are a kind of system that protects the Hell Express and are like "administrators" who prevent Regulars from doing unexpected actions.
Appearance and Personality
Gray Guardian is a monstrously large entity that bears an incredibly striking resemblance to Rak Wraithraiser, which the latter (as well as Khun and Baam) acknowledges. Its entire body is grey and it has completely red eyes.
Powers and Abilities
While its general abilities are unknown, it did require the efforts of eleven Regulars to take it down (although the fight lasted only briefly).