Miss Quill's arn
From Tardis Wiki, the free Doctor Who reference
Miss Quill's arn was implanted into her head by the Rhodians after they captured her. The arn made sure that Miss Quill was unable to use weapons and even lie to Charlie. (TV: For Tonight We Might Die)
Later, the Arn was removed by Ballon. (TV: The Metaphysical Engine, or What Quill Did)
