The hidden theme

I forgot to mention that all of last week's lists of ten things were inspired by enemies of The Flash. To wit:

• Ten things to do while visiting Glasgow: Mirror Master II
• Ten songs written or co-written by Lamont Dozier: Heat Wave
• Ten spells mentioned in the Harry Potter books: Abra Kadabra
• Ten places in the German state of Niedersachsen: Pied Piper
• Ten musical artists from Australia: Captain Boomerang

Why, yes, I am a nerd!