Nothing is worse than trying so hard to do the right thing, then discovering that it was the worst thing you could have done.
I wrote this final chapter to be a slight upswing in the plot so that we wouldn't end on such a sour note. No, I didn't kill Elend. I sure wanted you to think that I would, but I never planned to. I had always intended them to discover where the first Mistborn had come from when they reached the Well of Ascension, and this bead of metal is very important to the cosmology of Scadrial and, indeed, the entire overarching story of my books as a whole .
Elend was intended to become Mistborn from the very early stages of this book's development. So, I figured I ought to do something to him that would make him NEED to be Mistborn. Why did I want to make Elend Mistborn? I know it bothered some readers. I felt I'd explored his character as well I could in this book, and I needed something to upset the balance–tenuous as it is–that he'd arrived at here. He's not going to replace Vin–you'll see in the next book that Elend as a Mistborn doesn't change as much as you might think. But it does put him in new situations, and those situations allow him to progress as a character in the way I felt he needed to.
Anyway, this will make for a very interesting book three. Also, the mist spirit–now, maybe, you can see a little of what it was trying to do. It was struggling to find a way to get Vin to NOT go to the Well of Ascension. Giving hints to Sazed, scaring her, threatening Elend, pointing in the opposite direction. However, it is rather hampered in what it can do, as we'll find in the next book.