Maiden opposing key monster in myth - Crossword Clue, Answer and ... I believe the answer is: manticore 'monster in myth' is the definition. (mythical creature) 'maiden opposing key' is the wordplay. 'maiden' becomes 'm' (cricket abbreviation). 'opposing' becomes 'anti' (prefix meaning 'opposing'). 'key' becomes 'core' (both can mean majorly important). 'm'+'anti'+'core'='MANTICORE'