10 Things We NEED To See In The Rings Of Power
4. The Rise Of The Lord Of The Nazgûl
As the show title indicates the primary focus will be the forging of the Rings of Power. We also know it will focus on the War of the Last Alliance. Between those two events, Sauron gathered together the Nine Rings of Power, and gifted them to nine kings of men.
Given how huge the Witch-king is, as a character in the Lord of the Rings, it would be unthinkable not to show his corruption and fall to evil. Most of this will have to be invented purely by the show writers, however. Tolkien didn't divulge much of the Witch-kings character, origin or story before the first fall of Sauron. All we know was that he was a great king of men. So, bets on anyone who gets introduced as a "great king of men" becoming a Nazgûl.
The Lord of the Ringwraiths will likely not be referred to as the Witch-king in the show, either. This name was only given to him after the Battle of the Last Alliance, when he reappeared to found the Kingdom of Angmar, in preparation for Sauron's return.