So, it worked like every other of the 30+ waves of Lego Collectible Minifigures. Lego fans have also been begging for more castle/fantasy sets for years so the series was pretty much guaranteed to sell out when it was announced. I have a few of each figure myself because of the multiple heads/mix and match character customization element present in the series and I use Lego to play DND.
Although if they ever do release another series (Which I hope they do). The boxes aren't blind. There is a QR Code on the bottom and a companion app that tells you what you are getting.