No Gods, No Masters

 is a final quest in Fallout: New Vegas.

Clearing Hoover Dam

 * Enter the offices through last Hoover Dam Tower
 * Activate the switch to allow Yes Man to gain control of the dam in the control room.
 * On the same floor, go SW past the 2nd Tower exit (with the kitchen) and open the door to Hoover Dam Power Plant 1. It opens to a balcony with the switch that powers the East Power Plant on the western wall.
 * Go back topside to deal with the Legion and NCR on Eastern side.

After clearing the Hoover Dam, the Courier sets forth to the Legate's Camp for the final confrontation against Caesar's Legion. This is a very difficult fight against Legate Lanius and his troops.

If possible get all the equipment you will need before you enter the battle. This is also the last mission in the game (unless you're siding with The Legion).

After defeating him and his troops, you walk towards the gate only to be surprised by an explosion which stops your character from moving.

Detailed walkthrough
To do this you may go in guns blazing or simply take out the first guard and disguise yourself, then as you go up the steps you may want to save. You have two paths: one fight your way through legate leader or, if you have a speech or barter skill of 100, talk your way out, even a speech of 80 will work, you can just fail one speech option and bluff with a speech 80 in the next options (have in mind he is a very tough enemy and comes with three praetorian guards armed with ballistic fists but you get the bonus of his weapon and his mask for killing him).

If you choose to fight, you have several options. He does not become hostile until engaged in conversation or fired upon, so a few options are opened there. It is advisable for any ranged character to seed the only path he can run down heavily with mines. Even with a minimal explosives skill (as low as 25) a half-dozen plasma mines will blow him to oblivion. Melee characters can grab one of the Praetorian Guard's Ballistic Fists and use that against him, as they do excellent damage and the chance of knockdown aids in his easy dispatch. Characters with high ranged skills can open the fight with a shot from a high-damage sniper weapon such as a Gauss Rifle or Anti-materiel rifle and do significant damage to the Legate and his guards before they are in close range. It is highly advisable for any character build to have a close-range weapon such as a Plasma Defender, 12.7mm submachine gun or a high-damage melee weapon at hand as unless you have a preponderance of mines to cover the entire path liberally they will eventually end up at quite close range using their sword (the legate) and ballistic fists (the praetorians). If you are a melee-oriented character the use of the Ranger Takedown ability learned in Novac can make for an almost trivial fight, simply knock the legate over and proceed to bash his skull in with your weapon of choice.Another option is to take 5mm ammo and go to the ledge with the post and stack your ammo until you can jump onto the ledge. You should be able to take him out without a problem if you have a good weapon and enough ammo, specifically the Alien Blaster and a high energy weapons level will kill him in two to three shots. It is also possible to hit the Legate from the Brahmin pen located in the lower region of the camp, sitting near the entrance to the pen allows you to just about get his head in range, and so by using a sneak attack critical with the anti-material rifle it is possible to one-hit him without being close enough that the Praetorian guards can attack you. Another tip is when you first enter the camp AFTER the first guard, take a right and you will see the gate where Legate keeps his mongrels. You can choose to "repair" (sabatoge) it so they cannot create backup for Legate.

Once done proceed to the gate you entered through and once you walk up to it it will explode and heavy NCR troopers will walk in as well as the general who will talk to you (notice there is a fog behind the gate). You have a few options which will all clear the fog revealing your army with Yes Man leading it. Depending on your choice they will either kill the NCR or they will just let them walk away. Having speech and barter as high as possible helps here. Afterward Yes Man will tell you you've done well and say he's going to get an upgrade to be more assertive. Note that once you speak to Yes Man, the credits will roll telling the story of how you have done. After the credits are over you will be reset to your last save. Therefore, killing the legate and taking his mask is completely useless, unless you choose to fight the general in which case you may get a swipe or two in before the upgraded Securitrons reap their bloody harvest.

There is a humorous ending for the general if you pass certain speech checks. The option to have the general thrown off the dam will prompt a short scene where Yes man is atop the dam and throws the general into the dam (the general falls like a rag doll). After this you will be on the ground with Yes man which leads to the credits rolling.

Bugs

 * After you receive the briefing from Yes Man about what needs to be done at Hoover Dam, the game presents a pop-up warning about moving into the endgame. If you do not say that you want to move on to the end of the game, and leave New Vegas, this quest will not load and the gate to enter New Vegas will be locked, preventing you from getting back into the Lucky 38.
 * This is not exactly what happened to me, but I decided not to do it right away, and 35 hours later when i decided to do it, i couldn't. Someone in the IRC channel (Sinistrahd) suggested I try reseting the quest with the console, which I did. First I tried resetting this quest with no luck, then I tried resetting "You'll know it when it happens", talked to Yes Man, then reset this quest. This worked, so the sequence that worked for me was resetquest 00131F08 > talk to Yes Man > resetquest 00154233. I hope this helps others.
 * After selecting the option to move on to the dam, the game can crash to desktop if the player's timescale has been adjusted to anything but the default 30.
 * The courier is asked by Yes Man to pull the lever and activate the eastern part of the dam, if that lever has been pulled in the past the player will not be able to finish the game.
 * If you choose to run back out of the gate before facing the Legate, then you can fast travel from the area. Doing so causes you to be unable to fast travel from another location. This can be dealt with by walking into a building and back out, but you must do this every time to continue fast traveling.

Behind the scenes

 * The phrase "no gods, no masters" is a phrase used by famous anarchist Emma Goldman in her description of an ultimate society. The phrase was also later used by Ayn Rand.