I got an invite, but did not get a key or access to the Closed Alpha forum
I just read the ROUND THREE of Mirage Closed Alpha Test Begins Nov 17 posting, and saw this very same question in the posting. I got the e-mail invite a while ago, and never received a key to the Alpha.
@LaotianCommotion round 3 ended on November 20th and we are now working on round 4.
If you complete the NDA form that was part of the invitation email, you will be able to participate in round 4. I’ve sent you a direct message to try to work this out.