Hektor (Steam key/Region free).

http://store.steampowered.com/app/334070/
HEKTOR is a first-person, psychological horror game where nothing ever stays the same for long. Explore a world that literally moves with your every twist and turn, as corridors shift and change before your eyes. Uncover cryptic clues to help you find your way and elude the horrors that only madness can conjure.

You were a subject at HEKTOR, a now defunct, covert research facility buried deep beneath northern Greenland. Forgotten in its dark corridors with only a lighter and flashlight to guide your way, you must overcome a psychosis brought on by years of torture and confinement to escape.

KEY FEATURES
Second guess your every move as procedurally generated corridors alter the path you’ve come from or where you’re going.
Immerse yourself and explore the atmospheric military black site, HEKTOR, and uncover the terrifying secrets of its dark past.
Encounter a horrific monster that tirelessly pursues you, and avoid others that alert it to your presence.
Scavenge for pills to keep from falling further into your psychosis, as well as other items to advance toward escape.