Mod:Fallout: The Frontier/I Am Legion

I Am Legion is the first Legion quest, granted upon asking to join the Legion during A Bridge Too Far.

Quick walkthrough

 * Talk to and follow Callidus
 * Survive the unarmed beatdown by your fellow Legionnaires
 * Deal with Yuri
 * Kill Bizmark and Warren or talk your way around it (Speech 69)

Detailed walkthrough
After asking to join the Northern Legion during A Bridge Too Far, which requires high positive Reputation with the Legion in the Mojave, you'll find yourself transported to the Ostia Dungeons without any items and fitted with a slave collar. After a brief chat with Bizmark, you'll be asked to follow and obey Callidus. Openly disobeying Callidus at any time will result in the collar being activated and your head exploding.

Your first task: survive a beatdown from four unarmed Legion Gladiators. Callidus will hand you six Synthetic Healing Powders to use during the ordeal; a Barter 40 check will net you an additional four.

Next, you'll have to execute a captured NCR soldier named Yuri. He can't fight back, so this shouldn't be too difficult.

Finally, you'll be asked to kill your fellow Legion initiates, Bizmark and Warren; only one may join the Legion proper. Either do so, or with Speech 69 make the argument that further bloodshed's a waste of resources. Unfortunately for your fellow would-be Legionnaires, Callidus will simply detonate their slave collars personally, but he's impressed by your silver tongue.

Either way, you'll have passed your tests and be taken to Legate Valerius. Welcome to the Legion.

Rewards

 * 500 XP
 * Membership in the Northern Legion
 * Legion Recruit Armor (Snow)
 * 6-10 Synthetic Healing Powders