"For all seas, lakes, rivers, fountains and springs are in his government; so that the Elves say that the spirit of Ulmo runs in all the veins of the world."
i don't know if anyone has yet mentioned that the Wicthking could have escaped the same fate as the other nazgul.
When the one ring was engulfed buy the lava of mount doom the 8 remaining nazgul were destroyed but could the witchking's spirit not have been destroyed because he was killed way before the ring fell i think his spirit might have stayed on middle earth seeing that when he died his ring was no longer connected to the one ring unlike the other 8 who went into the void when sauron dies
i would like your opinon about this theory