After a recent preview session with the game, I'll say this: It's complicated. Dungeon Defenders doesn't just mix pieces of a few genres, it totally combines them. There is a full tower defense game here, and a full action-RPG game, and even a little bit of real-time strategy resource management. There's a lot going on, but just like recent genre-mixer Monday Night Combat, players who can juggle a few genres at a time will find a lot to like.
The tower defense side of the gameplay is most apparent at the outset. After choosing one of four classes (I played with the Mage and the warrior-like Squire; though was promised we'd hear more about the Huntress and the Monk soon), you're tossed into a story mode with a tower full of levels, each one requiring you to defend an "Eternia" crystal in the center of the map against waves of goblins, orcs and various other fantasy-style meanies.
In the "Build Phase" of each wave (which starts out a few minutes long, but shrinks as the level goes on), you can run around the map and place towers using your mana resource. Each class has its own towers, and the full 3D gameplay brings some fun into tower placement -- some towers use area of effect spells, some are simply barricades and others use the physics engine, throwing bowling balls down stairs or firing out spinning blades. Each tower is placed and positioned using the analog sticks on the controller; and while manipulating them was not simple, it was still intuitive, and I got the hang of it after just a bit of practice.
Combining the two genres leads to some interesting strategy options: Do you put all your towers on one side of the map and defend the other with your character; or do you spread out your defense grid and keep your character mobile, just in case something goes wrong? Periodic mini-bosses will tromp out with the horde, too, requiring you to put a little extra firepower in the right places. And if you find yourself overwhelmed, you can recruit friends. Dungeon Defenders features jump-in, jump-out local or online co-op for up to four players. While there's an obvious advantage to four players building defenses at once, when all four are hacking and slashing through the hordes as their towers rain down attacks, the chaos can be difficult to follow.
Fast-paced, complex and, at times, utterly overwhelming
The action-RPG elements also support the in-between stages of the game. Your created heroes are persistent and earn experience and gold that carries over between matches. You can also pick up items and armor from fallen enemies and looted treasure chests, which provide bonuses to characters' health, defense and attack stats, as well as resistances against certain kinds of enemy attacks. Some items even grant bonuses to your tower types, and all of them can be leveled up and traded between characters and players. Once you max out an item, your Gamertag (or other system ID) will be attached to it, so if you trade it along, anyone who's in possession of it in the future will know you were the one who put the work into it.
Packed with content, Dungeon Defenders is a fast-paced, complex and, at times, utterly overwhelming game. If you can handle that, it should offer an enticing mix of two very popular genres.