Like its predecessor, Orcs Must Die! 2 is a variation on a tower defense game. As either the War Mage or Sorceress in the campaign mode, the player must attempt to defend one or more Rifts from an onslaught of orc armies that emerge from one or more doors in a given level. The orc armies arrive in waves, between which the player is given time to recover and place additional traps; except for Nightmare difficulty, roughly every three waves includes a longer respite that lets the player determine when to release the next wave.