Dungeon Defenders - Basics

In each stage of Dungeon Defenders, you start by collecting Mana from chests, then you can build some Towers to protect the Eternia Crystal(s) from monsters that spawn from specific points. Now, there is a Build Phase and a Combat Phase. The Build Phase gives you unlimited time to make preparations for the next Combat Phase, by repairing/upgrading Towers or building new ones; note that you do have a timer before the next wave automatically starts on Insane/Nightmare difficulties. On the other difficulties, you start the next Combat Phase by touching the Eternia Crystal (on PC, there is a button you can press to start it no matter where you are in the level).