Related Clues:

• Foe hiding, in a way, in the puzzle's four longest answers
• Ill-wisher
• "No mortal could __ with Zeus": Homer
• Source of conflict
• The Axis, to the Allies
• Hatfield, to a McCoy
• Sentry's classification
• Be competitive
• One from the other side
• "Who goes there, friend or ___?"
• Cassius, to Caesar
• The FBI, to the mob
• Model oneself upon
• Grant, to Lee
• Life, in Lille