Red Barrels and the Humble Bundle are currently offering the Deluxe Edition of Outlast for free. Outlast was released back in 2013, is powered by Unreal Engine 3, and is described as a true survival horror experience which aims to show that the most terrifying monsters of all come from the human mind.
In Outlast, players take the role of the investigative journalist Miles Upshur as they explore Mount Massive Asylum and try to survive long enough to discover its terrible secret.
The Deluxe Edition includes the base game, as well as its Whistleblower DLC.
This offer will end in a day, so be sure to acquire your free copy while you still can. Those interested can get the game from here.