When province 7 opened up, I had already completed the prior missions to kill undead privateers and stegosaurians, and saw a new pair of missions appeared.
Then it disappeared. (Before I found any of those monsters or bosses; I forgot which ones they were.)
Is this a bug?
If it matters, I have yet to complete the 100 magical night stages mission.
Ok, kinda makes sense. If I recall correctly, the number needed was looking pretty excessive and not something I would bother farming for the avatars, unless I wanted to farm it on a daily basis, so my level of concern for it is fairly low, compared to the confusion about the teaser.
Thanks for the question, I was wondering the same thing and was about to contact SG . It would be sad to get the same avatar for all of the work required.