The are basically blind creators who can hear you moving around in the world and will attack if angered. Also if you chose to engage them they will call for back up, leaving players with the dilemma of whether to attack or sneak past them.
“Their purpose in the world is, think of the cameras in BioShock 1, but think of them walking around looking for you,” explained Creative Director Ken Levine.
EGM’s TAKE: Your not going to be able to step two feet in this world without running into something massive that wants to kill you, which is good as it adds increased tension to the game. Now it’s not just a Big Daddy you’re trying to avoid, it’s multiple massive enemies who are all looking for blood. You’ll need to keep a lot of different strategies up your sleeve if you’re going to take them all on. There’s just something unnerving about how the Boys of Silence look.