The Shootist

Sudar wants you to kill Phost'Benon, then use his access card to open a Bane storage locker and bring back the weapon it contains.

Kill Phost'Benon

 * Phostbenon's [sic] Access Card 0/1

Acquire the Experimental Weapon

 * Bane Energy Rifle 0/1

Briefing
Sudar:
 * I don't really know how this works and all, but if you could just, you know, take that guy out or whatever, then come back, that would be cool. Buhmoni is pleased with the wepons you've brought back, but while he's studying them I have another taks for you. This one is as important as they get. The Lightbender who is considered their deadliest gunman, a beast we call Phost'Benon, the ghostly shooter, is out testing some more of the rifles with his personal marksmen.


 * Eliminating him would be a great blow to the Bane army. You can find him near Casso, and if you can, take him down.


 * Once he's eliminated we'll need you to find an access card that he carries with him. With it, you'll be able to access the Bane storage lockers inside one of the Bane's foxholes. Bring us back the weapon he has stored inside it. It's his personal backup weapon. It'll make a great addition to our trophy room.

Debriefing
Sudar:
 * Perfect. I can't wait to see how they deal with their best gunman being gunned down outside his own facility. Hahaha!

As per the briefing, Phost'Benon can be found outside the Casso Weapons Facility (a.k.a. Energy Weapon Center). He spawns at the south east corner of the building.

Once you have retreived his keycard from his corpse the weapon can be found in a crate at the south west corner of the same building. Contrary to the briefing it isn't in a foxhole.