Immortal Defense is a story-driven tower defense game in which you give up your body and life to become an immortal "path defender", and defend your home world from destruction, forever. The game takes place over millions of years. Is there anything you would give up everything to defend?
Open the Steam client, login and locate the Games tab on the top menu. Click this and then select “Activate a Product on Steam…”
Enter your unique code that's displayed on the 'Orders' page of CDKeys.com and follow the prompts to activate.
Your game is now viewable in the “Library” tab and is available to download/install when you’re ready. You can find additional support for the Steam client here: https://help.steampowered.com/en/wizard/HelpWithSteam