ME Riddle (again grrrr ; )

King, witch, Lord,
One who would sow great discord.
    Though fearful he was, some would sing
       that all his power came from his ring.

Just tried Sauron, which failed also. I've tried Murazor, Witch King, and Er-Murazor to no avail. Any more insight before I just give up?

Shawn --> Frustrated ; )