You think Tower Defense games are all about building? You thought wrong. Sanctum is not your average Tower Defense title. When the havoc starts, you get to join the fray! As one of the world’s first First Person Shooter - Tower Defense games, Sanctum has taken the best of both worlds to deliver an epic, one-of-a-kind experience.
Key Features:

Don’t just build towers. Build mazes!
Your way or the highway? The Customization System lets you have it all!
4-player co-op support; why double the trouble when you can quadruple it?
87 Achievements
Hidden Secrets & Easter Eggs. Have meta with your metal!

Note: I will send a friend request to the winner through Steam so I can send the key via chat, I will also send you a mail to tell you you won, good luck everyone :)