a threat that hangs over us like a/the 'sword of Damocles'
Freedom of expression can be a 'double-edged sword'.
(..) - You buried the elf? - Yes. And brought me here. You are... Pretty unusual, is it? How did you come by the sword? It's complicated. Why did Bellatrix Lestrange think it should be in her vault at Gringotts? It's complicated. The sword presented itself to us, in moment of need. We didn't steal it. There is a sword in Madam Lestrange's vault identical to this one. But it is a fake. It was placed there this past summer. And she never suspected it was a fake. (..)2011 Harry Potter and the Deathly Hallows: Part 2