Harry Potter novels et al

• Deadly sins and hills of Rome, e.g
• Literary gables and others
• Seven-player pieces
• The seas and the dwarfs, e.g
• Trios plus quartets
• Disney's dwarfs and others
• Groups like Disney's dwarfs
• Beethoven's Opus 20 and others

Wiktionary Word definitions in Wiktionary
n. (plural of septet English)