I think this might be related to the warframe ARG, they added some text to the steam listing saying:

ᴀɴᴏᴛʜᴇʀ ʀᴇᴡᴀʀᴅ, ᴄᴏᴜʀᴛᴇꜱʏ ᴏꜰ ᴛʜᴏꜱᴇ ᴄʟᴇᴠᴇʀ ᴛᴇɴɴᴏ ꜱᴛɪʟʟ ʜᴀʀᴅ ᴀᴛ ᴡᴏʀᴋ. †hê §ïgñål ï§ §þrêåÐïñg

Less related, but Unreal Tournament and Unreal Gold are also free. https://dormi.zone/post/3413855