Curses!

[The Saucepan Man]

And how are free will and curses intertwined?

Ah now, that one's a biggie.

As I recall, there is quite a good discussion of this issue in the context of the curse laid on Hurin and his family here:

Hurin and despair

Edit: I hasten to add that I am not suggesting that discussion of curses in the context of free will should not continue here. I am merely providing the link as it is relevant to the issue raised.