Possible Clues:

• Armageddon
• It brings everything to an end, upsetting mood with talk about old Penny
• Judgment time
• The end of the world
• End of the world
• Powerful Superman villain
• Miserable, sad and moody way the world ends?
• End of the world, Last Judgement
• Moody ads for time of the Last Judgement
• Calamitous time