The Lurking Fear is a secret level of Episode 2 of the AMC Squad. It can be accessed through Far Mountain Reaches. Once completed, it can be selected from the map screen. When you beat the level from Far Mountain Reaches, it will takes you to Dark Truths. Though if selected from the map screen, you will be returned to Base once level is completed.
Gameplay[]

Collect the weapons and ammo. On the right up the stairs there is a timed switch. Hit this switch and go through the door to the courtyard. You'll hear a mysterious disembodied voice speak an urgent message to you. Prepare for an ambush. After this fight, go to the central teleporter. You will be teleported to the Abyss dimension again. Fight off berserkers, ogres, demons, and finally the Abyssal Overseer. After the Abyssal Overseer is dead, you will rescue Eva Lockwood. Then you'll be taken to Dark Truths (Or if you played it from the map select screen, will return to base).
Weapons & Artifacts[]
Nemesis Staff (Weapon, Sang): standing right in front of you as you open the very first door. This weapon will be replaced by James' slot 0 weapon in subsequent playthroughs.