Layers of Fear: Masterpiece Edition free with Twitch Prime
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https://twitch.amazon.com/prime/loot/madden?tag=phtwllt-20
Twitch Prime is a service that is included with your Amazon Prime account. All you have to do is link your twitch and amazon prime accounts (amazon owns twitch). Monthly they give out free games and free dlc for games, you do have to play them through the free twitch client though, not through steam. The link above has info on all of their current promotions.
Layers of Fear is free from 10/24 - 11/1, as long as you claim the game before that time you get to keep it.