The words given all belong to well-known groups of seven. Sorting them into these groups reveals that exactly six members are listed, with one missing. The groups are:
- Colors of the Rainbow
- Blue
- Green
- Indigo
- Orange
- Red
- Yellow
- MISSING: Violet
- Harry Potter Books (last word of the title)
- Azkaban
- Fire
- Hallows
- Phoenix
- Prince
- Secrets
- MISSING: Stone
- Seven Deadly Sins
- Gluttony
- Greed
- Lust
- Pride
- Sloth
- Wrath
- MISSING: Envy
- Seven Dwarfs
- Doc
- Dopey
- Grumpy
- Happy
- Sleepy
- Sneezy
- MISSING: Bashful
- Seven Continents
- Africa
- Antarctica
- Asia
- Europe
- North America
- South America
- MISSING: Australia
- Seven Wonders of the Ancient World (locations)
- Babylon (Hanging Gardens)
- Ephesus (Temple of Artemis)
- Giza (Great Pyramid)
- Halicarnassus (Mausoleum)
- Olympia (Statue of Zeus)
- Rhodes (Colossus)
- MISSING: Alexandria (Lighthouse)
- G7 Member Nations
- Canada
- France
- Germany
- Italy
- Japan
- United Kingdom
- MISSING: United States
These missing words all are unique lengths and fit neatly into the blanks given.
Reading the letters above numbers in numerical order gives HEAVENLY VIRTUES, which is another group of seven and the answer.