Legate Lanius

Lanius is Caesar's Legate, living in the Mojave Wasteland in 2281. If the player chooses to side with NCR or doesn't side with either NCR or Caesar's Legion, he is the hardest foe to eliminate during gameplay.

Background
Asking Caesar about the legate reveals that Lanius was a member of a tribe hostile to Caesar's legion and Lanius was a bloodthirsty champion of the tribe, sometimes ambushing whole groups of soldiers by himself. When Caesar's legion was attacking his tribe, they knew that they would not be able to win so they sounded the surrender alarm, driving Lanius insane with anger, resulting in beating the Chieftain to death which caused his tribe to turn hostile to him. After taking out fifteen of his tribesmen, Lanius woke up in a bed with most of his face torn off, Caesar showed him the mask he had forged for him and offered him a place in his army.

Interactions with the player character
If siding with Legion, Legate Lanius will be the one who gives the final order to the Courier, and also the one who congratulates him after the battle. In all other cases, Lanius is the final opponent.

At the battle of Hoover Dam, if against the Legion, Lanius can be convinced into surrendering with numerous Barter and Speech checks, respectively 55, 65, 75, 85 and 100. Convincing him that the vast territory of the NCR is its weakness and that the Legion will not be able to claim and hold it. It is also possible to take a different speech angle to convince him to leave, suggesting that his fight was too easy because a trap lies in wait for him, and that you are only telling him this because it would be dishonorable to defeat a foe in such a way.

It is possible to kill him in one shot before he notices you, bypassing the conversation entirely. Before he talks to you he will appear as a friendly, however. With high enough (Good) karma or speech there is an option to have him fight you alone. The player may also make use of a glitch spot to snipe from in order to kill him easily. One glitch spot that i found is on top of a tent next to the grinding stone.You must jump onto a barrel and then jump onto the tent, the Legate is in view if using a sniper rifle or scoped weapon.

If Caesar is killed during the quest Et Tumor, Brute? Lanius will take over the role of "Caesar".

Appearances
Lanius appears in Fallout: New Vegas. He serves as the final boss of the game during the final battle at Hoover Dam, unless you side with the Legion. He is carrying the Blade of the East.

Behind the Scenes

 * "Lanius" is Latin for "butcher." "Legates" ('legatus/legati' in Latin) were generals in the Roman Empire, equivalent of the modern general officer.
 * He constantly mentions Mars, the Roman God of War, and claims that his name (Lanius) comes from the Son of Mars, being Caesar himself.
 * Strangely, while it is mentioned that his face was torn to pieces, under his mask he has no injuries but it may be a story invented by Caesar, or more likely the game developers simply didn't bother creating a new face model for him as it is unlikely the player would see him under the mask anyway.
 * Though it is implied that Lanius is a savage with no love for the Legion (by Caesar no less). Through dialogue if confronting him in 3 of the 4 major outcomes, it is shown that he does care about the legion and is wiser than his reputation suggests. Though brutal he seems to have a sense of honor as he disaproves of the Frumentarii and the plot with the Omertas to gas Vegas. This is also shown if the Character has a good karma level, he will agree (if the correct dialogue is chosen) to one on one combat.