The second part of the Faeries Ruin Plot is a set of tasks released with Chapter 4. In this part of the plot you have to make three pegs move through colored doors to get the key and then escape from Castle Nox. This is kind of hard to get used to how it works. I suggest looking at this guide on a Neopets pet page for help.
Task 1: We All Scream - Everyone loves an ice-cold bowl of Chintzy Mynci... even Hubrid Nox.
To complete this task you have to get all the pegs joined together (they join when they meet on the same space) and then move them to the ice cream square. This achievement does not show up until you then escape the castle.
Task 2: Fort Nox - There's gold in them thar halls!
This one is received when you complete a random sequence of knobs when moving around on the basement level. Just keep trying different moves and it will pop up at the top of the screen when you are successful.
Task 3: And One For All - "After you." "No, after you." "No, I insist! After you."
This achievement is received when you escape from Castle Nox with all the pegs united together. This is easy to get at the same time as you get the ice cream one.
Other Parts of the Plot:
Part 1: The Artefact Thief