Possible Clues:

• Hellish
• Gloomy, staying unsettled
• Gloomy
• Outstaying underworld runner
• Staying terribly dark and gloomy
• Where the pigs are, the nag comes up around one to make it dark
• Very dark (poetic)
• Gloomy or murky after the river Styx
• Nasty giant, somewhat gloomy
• Greatly gloomy