Lieutenant

The Lieutenant of the Master's Army (sometimes called Lou Tenant, or simply Lou, by the less mentally capable men under his command) is the right hand of the Master and the commander of the Mariposa Military Base.

Background
The Lieutenant is the model super mutant: Faster, tougher, and more intelligent than standard humans. He was the strongest of his batch, capable of withstanding the regimen of the FEV transformation without losing his intellect and skills (possibly even receiving an increase). His transformation created a sense of religious awe in him, focused on the Master and the Unity. He became his most devoted follower, supporting his master's ideals and firmly believing that the super mutants shall inherit the earth. For his devotion, he was rewarded with the highest position in the army, cybernetic implants, and personalized equipment. The Lieutenant is unlike any other super mutant in this aspect: He bears the pauldrons of what apparently is power armor, has an eye prosthetic and cerebral implants, and what seems to be an apparatus pumping his body full of stabilizing drugs, to contain the severe viral overdose contained within that would otherwise cause his body to tear itself apart.

In terms of personality, the Lieutenant is further unlike any other mutant. Soft spoken, urbane, and well read, his firm belief in the superiority of super mutants borders on conceit. Yet he believes it is simple honesty, for the super mutants are truly better adapted to the demands of the post-nuclear world.

Yet for all his intelligence and refinement, there are darker sides to the Lieutenant's personality. Though he considers torture crass, he finds it only satisfying. Unlike regular sadists, he does not employ it needlessly, especially if he can obtain the knowledge through normal coercion.

Fate
The Lieutenant ultimately perished, though whether he fell at the hands of the Vault Dweller or died in the destruction of Mariposa remains unknown.

Quests

 * Destroy the source of the Mutants.: The Lieutenant is an optional encounter on the fourth level of Mariposa. He provides information on the Master's plans and can be killed to ensure his demise. Killing him will allow the player to pilfer his locker, which contains the nuke key that can be used to unlock the nuclear bomb console beneath the Cathedral.

Other interactions

 * Harry will take the Vault Dweller to the Lieutenant if they allow him to. The Lou will then interrogate the Vault Dweller concerning the location of their Vault. Divulging it will lead to dipping and conquest of Vault 13.
 * Sneaking up on the Lieutenant (simply coming near his room will suffice) allows the Vault Dweller to overhear a conversation between VanHagan and the Lou concerning their imminent discovery of Vault 13. This is worth 1500 experience points.
 * Killing the Lou will trigger an unique death animation:

Appearances
The Lieutenant appears only in Fallout and mentioned in the Fallout: New Vegas add-on Dead Money. In Fallout: New Vegas, during G.I. Blues, Roy and Wayne will have an exchange where the former corrects the latter that the attackers called their leader Lieutenant, not Lou Tenant, and state that the boy can be "dumber than a mutant."