Crack of Doom

The phrase at the crack of doom, meaning "at the striking of the fateful hour", appears in Macbeth by William Shakespeare and has entered common usage.

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In J.R.R. Tolkien's fantasy world of Middle-earth, Tolkien puns upon Shakespeare's phrase; the Cracks of Doom (or Crack of Doom), are physical cracks - fissures within the great volcano Mount Doom - and are the very place where the Dark Lord Sauron created the One Ring. They also are the place that the One Ring must be cast into in order to be destroyed, thereby destroying Sauron.