|The following is based on Fallout: Brotherhood of Steel and has not been confirmed by canon sources.|
Rhombus, along with his men, entered Los and stole the Vaults' main laboratory keycard from a cult organization. He and his men fought the cult, but lost to them, so he was captured and taken to Los' torture chamber near the docks and was tortured by Blake for the location of the stolen keycard. Having hidden it under a truck, Rhombus later assists the Initiate to its location. Once in destination however, he is blown up by a ghoul suicide bomber.
Unable to continue fighting, he gives the Initiate the keycard and entrusts him with the task of stopping Attis' army and finding the Secret Vault entrance.
In the Residence hub, the keycard is taken from the Initiate by Attis, right after Defeat Mutant General. The card is essential to progress and Patty tasks the player to retrieve a copy during Find Laboratory Key in the Secret Vault - Ruins from a Vault scientist, Dubois.
Key to enter the Secret Vault - Laboratories.
- Rhombus, given to the Initiate at the end of Escorting the Paladin (taken away again in Defeat Mutant General)
- Dubois, and a little later on, a deathclaw in the Secret Vault - Ruins Cave.