Father Elijah

Father Elijah is the main antagonist of Dead Money and a former elder and leader of the Mojave Chapter of the Brotherhood of Steel

Background
He went missing during the NCR takeover of the HELIOS One powerplant and was never found (Although you later find out, with the DLC Dead Money, that he is located at the Sierra Madre). According to Head Paladin Hardin, his becoming an elder was questionable due to his status as a scribe; normally, the ability to become an elder is reserved for Paladins, though in Elijah's case an exception was made due to his high intelligence. Veronica refers to him as still alive as he contacted her after the HELIOS One defeat.

During the quest Still in the Dark, after talking to some of the members of the Brotherhood of Steel, you find out Elijah became an elder because he was a genius. However, the members say he was a strange man and his battle tactics were poor. They then tell you that during the takeover of HELIOS One he held them inside the building too long, causing most of the Brotherhood to be killed by the NCR. He kept saying "something was almost ready". This was most likely referring to the Archimedes II.

Dead Money
In the add-on, Dead Money, it is revealed that Elijah founded the Sierra Madre whilst running from his failure as HELIOS One, he went insane over trying to unlock the casino's vault and gain access to its awesome power, and has been luring wastelanders to break into the vault for him with the casino's radio signal. The Courier is knocked out by toxic gas in the Abandoned BoS Bunker and wakes up in the city of the Sierra Madre with an explosive slave collar on their neck, and is instructed by Elijah to find the three others he has captured so you can work together.

At the end of the campaign, the player finally meets Elijah face-to-face in the Sierra Madre's vault chamber, where he intends to kill the Courier even if they had obeyed his every instruction. Elijah hides behind a force field and activates five very strong wall turrets. When the turret above where Elijah is is destroyed, the explosion will short out the force field and he will attack the player personally. He's not much stronger than a normal human, and when you kill him all the turrets will explode and the vault will start a self-destruct sequence.

After killing or locking him up, his terminal in the Abandoned Brotherhood of Steel Bunker will contain a holo-message which says that it is for Veronica. Talking to Veronica after this will result in a new conversation that also gives her a special new perk.

Appearances
is mentioned in Fallout: New Vegas, and appears in the Dead Money Add-On.