Nope, they won't be called "Mystery Boxes" for realz. This was sort of a pre-announcement, we'll have more details that follow.
They contain some solid basic stuff and a chance at some rare awesome stuff.
Why do 'em? Because the average playstyle in betas (not ours, just any beta) is to play long enough to decide if you want to buy/preorder or not and then stop - but we want as much testing/feedback as possible right up through launch, so this lets us incent more actual testing where you don't feel like your time is totally "wasted" knowing that your character progress won't carry over from beta to live - well, at least this is a kind of progress that can benefit you post-launch.
They're per account AFAIK.
We can use these as rewards for anything we feel so inclined, before beta and after live, to thank those who help us in various ways, apologize if we have big downtime, etc.
And nope, they aren't a secret trojan horse for microtransactions.
They're just freebies.
