I am dumbfounded. How do I even unlock these four achievements? All I got as a hint is a questionmark. For each one. At least the other hints gives you, you know, a hint? I tried to figure out a way for Nel to gain Faylen's body but no such luck. So, there must be something? I can only assume it has something to do with the portal world?
From what I've experienced so far, hints for the unlabeled achievements become available after you have completed certain other events, such as other achievements. My advice is to just keep playing as usual, and you'll hit them eventually.
The four you show are all connected to the cursed citadel in the dark world. I already had them completed when I started it up.