Caesar's Foe

Caesar's Foe is an unmarked side quest  As of patch 1.4.0.5xx it is now a component of the larger Faction Hit-Squad Master Quest, along with the anti-NCR quest Most Wanted.

Overview
Caesar's Foe is the name given in the G.E.C.K. editor to the quest which controls the appearance of legionary assassins. Should the Courier's negative reputation with Caesar's Legion reach a certain point, legionary assassins will be dispatched to kill them. As of patch 1.4.0.5xx, this quest has been dismantled and replaced with "Faction Hit-Squad Master Quest," with the same in-game function.

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.

Locations
Legionary assassins repeatedly attack the player close to locations such as Ranger Station Charlie, Grub n' Gulp rest stop, Chance's Map, Wolfhorn ranch, the emergency service railyard, Followers Safehouse, Jack Rabbit Springs, and Vault 11.

Bugs

 * Previously, this quest would only cause legionary assassins to appear once. Due to scripting errors, any further appearances of legionary assassins would not be triggered, regardless of the Courier's location or reputation with the Legion. This issue has been fixed as of patch 1.4.0.5xx.
 * If Boone is not a companion, wearing Legion faction armor before the assassins are able to see the player character will result in the decanus engaging in dialogue with the Courier, saying that they are marked for death. As soon as the dialogue ends, the hit squad will stay still, allowing the player character to kill them one at a time with melee sneak attacks, given the player character can kill the assassins with one sneak hit.