This page of our Control guide contains a walkthrough for Old Friends - one of the side-quests found in the game. You will learn, e.g. how to defeat all 6 elite enemies and get 6 pouches.
To start the quest, talk to Arish in Central Executive.
Walkthrough: You need to get six pouches that belonged to Arish's men. Remus can be found in NSC Energy Converters in the Maintenance.
Guy is in Atlas Chamber in the Maintenance. He is accompanied by many opponents, so start with eliminating them.
Another sought character, Cho, is in Ventilation in the Maintenance.
Hazzard is in Black Rock Processing in the Maintenance. Wears heavy armor and uses a grenade launcher.
The final two enemies, Hepstonall and Thompson, are in Blackrock Quarry and NSC coolant pumps in the Maintenance.
Arish will reward you with some modifications, crafting materials, and 4 skill points.