Caesar's Foe

 is an side quest in Fallout: New Vegas.

Overview
Caesar's Foe the name given in the GECK editor to the quest which controls the appearance of Legionary assassins. Should the Courier's negative reputation with Caesar's Legion go high enough, Legionary assassins will be dispatched to kill him.

Legionary assassins are dispatched within hours of the Courier first attaining a sufficiently negative status with the Legion. Thereafter assassins are dispatched approximately every three days, depending on whether or not the Courier is located in an area where they can be attacked.

Bugs

 * Currently this quest will only cause Legionary assassins to appear once. Due to scripting errors any further appearances of Legionary assassins will not be triggered, regardless of the Courier's location or reputation with the Legion.
 * A third-party fix for this, as well as bugs in Caesar's Favor and Caesar's Hire, can be found here: New Vegas Nexus