To tell you the truth though, the whole thing about the liquid metal lake went over my head when I read WoA. Just wasn't obvious enough I guess. By the end of WoA, everything was moving fast enough that even the connection between what Vin and Elend find and what Fedik found wasn't clear for me.
I have to agree with you there. I didn't even notice any mention of a liquid-metal lake. That would be a neat idea with a clear liquid metal as mercury's alternate. Although, the liquid metal could also be casium, francium, gallium, or rubidium which are all liiquid at or around room temperature....
That would be quite a sight to see, a whole lake of liquid metal. Brings quite a neat image to mind.
Why was it that Vin could release Ruin?
I think we are asking the wrong question here. I think we should be asking why she was chosen by Ruin not why she could do it at all. I think that anyone with either hemalurgy/feruchemy/allomancy or any combination of the three could have released it. Alendi was the one chosen by the well until Rashek decided that that would not do. So, now Rashek goes to the well and can either release Ruin or take the power himself. He takes the power himself and effectively bests Ruin for a thousand years or so. So either I'm completely crazy or we should look at the angle as to why Ruin wanted it to be her and not someone else like Zane or anyone else...