Orcs Must Die! Unchained gets more content in a fairly large upcoming update with the version 2.7. This update includes a new campaign with survival mode and more than 50 challenges.
Three new maps are included in survival mode. When it comes to traps, there will be a large selection of new ones with a tweaked and reworked interface. You can view the full list of changes here.
Orcs Must Die! Unchained, the tower defense meets third person shooter hybrid is available for free on PC here.
Source: God is Geek