Hello there fellow gamers! 
The Callisto Protocol is free to own forever.
As long as you claim a copy before 15:00 UTC on the 29th August.
Survive to escape the horrors of Callisto. Using a unique blend of shooting and close-quarters combat, players will need to combat rapidly evolving creatures while scavenging to unlock new weapons and gear to outrun the growing threat of Jupiter’s Dead Moon.
Enjoy!