No Gods, No Masters

Upon arriving at Hoover Dam, navigate north-east across the dam's top, past the Visitor's Center. Allies like the Khans (if allied) or Boomers may assist. Avoid or eliminate hostile Legion and NCR forces.

Reach the Hoover Dam Offices. Deal with any NCR Troopers or Legion infiltrators.

Locate two NCR Heavy Troopers guarding a door. You can either fight them or pass a Speech 75 check to have them leave.

Inside the guarded room, find the terminals. Install the Override Chip and choose your objective: "Send Power to the Fort" to activate your Securitron army, or "I want this dam out of operation" to sabotage the dam.

If sabotaging the dam: Head west to Hoover Dam Power Plant 01. Eliminate any hostile NCR. Find the West Power Plant Control Box on the east wall, activate it, and select "Overload and blow it up!". Note that NCR in the offices will become hostile, but you won't gain Infamy for killing them.

If activating the Securitron army: Find the door to a Hoover Dam Power Plant on the eastern side of the Offices level. Turn west and find the East Power Electrical Switch on the wall. Activate it.

After setting your plan in motion, return to the Hoover Dam Offices and find a door to another Hoover Dam Tower on the eastern side, leading to the eastern end of the dam.

Back outside, follow the dam south-east. If you completed 'For Auld Lang Syne' and allied with the Khans, they will assist. Securitrons will also join your ranks.

Cross a ruined bridge east to reach The Legate's Camp.

Enter the camp and head east, dealing with Praetorians. Ascend stairs at the eastern end to find Legate Lanius.

You can fight Legate Lanius, who is accompanied by Praetorians. He wields the Blade of the East and wears a Legate Helmet. He will flee and attempt to heal if injured, then re-engage.