Unclean (Forgotten Realms: The Haunted Lands, #1)

Good.
You understand now.
I am not your beloved anymore.
I am
unclean
Foul, and a slave to creatures fouler still.
Please...
please...
destroy me if you can.

The realm of Thay has long been ruled by the uneasy peace of an alliance of wizards, but all along there has been one who believes he is the true master. And when that one wizard finally moves against his former allies, his homeland could be only the first of his conquests.