Defender Sibley

Defender Sibley is a member of the Brotherhood of Steel Outcasts located at the Outcast Outpost in Bailey's Crossroads in the year 2277.

Effects of player actions
He takes the player to Olin and the Pod when he's told to do so, and once the player completes the Anchorage Reclamation simulation and opens the locked door to the armory, Sibley will attempt a coup d'etat with his men against Protector McGraw, feeling that the player doesn't deserve anything in the chamber.

Appearances
Defender Sibley only appears in the Fallout 3 add-on Operation: Anchorage.

Behind the scenes
Brotherhood members Sibley, Olin, McGraw, and Morrill, all of whom appear in the Operation: Anchorage add-on for Fallout 3, appear to be named after buildings on the campus of Cornell University, including Sibley Hall, Olin Hall, Olin Library, McGraw Hall, McGraw Tower, and Morrill Hall. Unlike other cases of "easter egg" names like Lulu and O-Dog (whose names are references to real-life businesses located where those characters spawn), it is unclear why these Brotherhood members would be given Cornell-themed names.