To get the Traveling Maiden Set, you must first reach Mountaintops of the Giants, which you'll do shortly after defeating Mohg, Lord of Blood in Leyndell, Royal Capital. As you get to this zone ...

When is the Elden Ring Nightreign release date ... The flavor text of the Nox Swordstress Crown and Night Maiden Twin Crown reveals they live “in eternal anticipation of their liege.