Orcs must be shot, burnt, stabbed, crushed, impaled, frozen, catapaulted, dissolved in acid, turned into chickens, or forced to murder each other. They must die, and specifically they must die between leaving a large set of double doors and reaching a magical portal. You can cause this through a combination of placing traps and shooting them yourself. In fact, you must.
Orcs Must Die 2 is a cross between a tower defense game and a third person shooter, and like its predecessor, it is excellent. This is not a coincidence: it’s a bunch of new enemies, traps, weapons and game modes for the same underlying game. The major change is what felt like Orcs Must Die’s most obvious omission: 2-player co-op.