So you want to join the guild Nightmare Knights?
To join NK you need to be at least level 60. Beyond that you should definitely read our codex as it's the basic tenants that we believe in. It's also a good idea to have a strong reference so we know that you are someone who is trustworthy.
Once you feel you have met all of these needs then contact one of the Circle of Light council members and request an interview. They will ask you a series of questions and post the dialogue for a vote. Please note that we require 2k per month in the form of guild dues to pay for things like our guild hall and supplies for guild hunts. These are responsibly stored and kept but are a requirement of NK.
You will know if you made the cut usually within a week but we are busy so it could be longer. Good luck!