The power of the Ring could not be undone.

Sauron's warband size is increased to 24. Additionally, a force that contains solely of models from the Barad-dûr army list will never be considered Broken if Sauron has 3 or more Wounds remaining. Should Sauron have 2 or fewer Wounds remaining, the army will break as normal. Should Sauron be slain, the army will immediately count as being Broken.