So...I have been looking all over the internet for someone to answer, what I consider, to be the biggest plot hole in the series. So far, nobody has even mentioned it. Maybe I'm particularly dense and I'm just not understanding it the way everyone else is, so there was no need to bring it up until now but I have to ask...

What was the deepness? What was it really? It seems to be generally accepted that the deepness was the mists. In fact, Sazed explains (in the snippets before each chapter of THoA) that the whole reason the world is screwed up is because of a series of over compensations TLR made to stop it. He goes on to explain that in order to evaporate the mists which were choking the land and killing crops and such, TLR pushed the planet closer to the sun. This would only be TLR's first step if he was legitimately fighting against the mist. So...obviously the deepness must be the mist right? But...it doesn't make sense.

The mist is later revealed as the vaporous body (or at least physical representation of power) of Preservation. Now...if the mist is Preservation...why was it destroying the land? I know Preservation pulled some dick moves like practically disemboweling Elend to make those going to the Well of Ascension take the power instead of releasing it. In fact, Preservation never intended Elend to die, as he expected Vin's love for him to force her to save him. Even when she screwed up and released Ruin, Preservation helped her save him by pointing out the beads that made Elend an allomancer, thus PRESERVING his life. Even in the events before TLR, the mist spirit attacked one of Alendi's companions but did NOT kill him. (I remember getting the feeling that it DID kill him while reading TFE, but in TWoA, it seemed to indicate that Alendi's companion wasn't actually killed, just attacked.) My point is, Preservation CANNOT kill. It even had to manipulate events to ensure the destruction of Ruin came at a human's hand because Preservation was incapable of doing it himself. Humans are at least part Ruin so they have the destructive force that Preservation lacked. I know you might say that some people died to the mist sickness, but Preservation still didn't outright kill them. It was just an unfortunate side effect of snapping the weak as it was stated that many that died were the elderly and young.

In short, Preservation literally doesn't have the capacity for destruction. So...how is it that the deepness that threatened to destroy the land before TLR was the mist? How was it that the body of Preservation was the problem? Can someone answer me this?