I have a theory... so the creators said on a podcast that we saw the monster this season, but they also said "... but (we) may not have realized it".
I've already put this on the linear board, but one of my theories based off this statement is that the "monster" is really a person. Walt fits the profile with his "gifts"... his powers yet so far always manifest themselves in some negative way (killer polar bears, killing rare birds, talking backwards real creepy soaking wet... you know, negative). I don't think Walt is evil, and I certainly don't think he wants to be... I just think he has the potential to be, making him a very dangerous, caged monster.

I have a theory... so the creators said on a podcast that we saw the monster this season, but they also said "... but (we) may not have realized it".
I've already put this on the linear board, but one of my theories based off this statement is that the "monster" is really a person. Walt fits the profile with his "gifts"... his powers yet so far always manifest themselves in some negative way (killer polar bears, killing rare birds, talking backwards real creepy soaking wet... you know, negative). I don't think Walt is evil, and I certainly don't think he wants to be... I just think he has the potential to be, making him a very dangerous, caged monster.I don't think Walt is the monster. Not trying to belittle your theory but I just don't.

I think we saw the monster when we saw what was thought to be Sayid's smoke signal. Why? Because we never see Sayid with the leaves or light a fire. All we see is him busy checking out the village. I think the smoke was the monster and not Sayid's signal to Jack.

Danielle said that the monster was the island's security system. We are assuming that this system had been in place long before Walt arrived. So no, Walt isn't the monster.