Different from other ghosts, they both have a slight more anthropomorphic physical, although still don't having arms or legs. Just like their son, they possesses a totally white and translucent skin, wearing props like transparent veils, cloaks and capes. Gloomira has a veil trought her armless body and Illus wears a cape, plus having a "second face" behind his head.
Gloomira and Illus are benevolent and pacific civilians and responsible and concerned parents the most of the time.
Gloomira's most notable characteristics is her humility and loyalty, being confidential yet prospect over her family and friends. Illus have a very stoic, distant yet "open" personality, usually supporting his wife and son, but looking hopeless and worried in relation of Mourelai and Ardabur.
Napstablook is the couple's son.