The Red-faced Monster appears in "Blood Under the Skin." Crying, she picks up Finn and thinks he is her baby after Finn runs out of the Swamp of Embarrassment with a red face. She tries to get Finn to nurse, which he emphatically refuses. Jake manages to sneak Finn out of the monster's grip. No one truly knows why she was crying, but it is probably because she lost her baby. Her baby is never revealed in any episodes so far.
Red-faced Monster is similar to a yeti with a white fur and a red face.