Well, to say it briefly, they aren't free.
I got a full one pack for my stake, but had to pay 1 of the in-game Credit to claim.
The minimum amount I was able to buy were 1000 Credit (for 4 HIVE).
I need a potion to open the pack, which costs 150 Credit.
No problem, got 999 of them left.
The minimum spend in the market is 1000 Credit.
That's where I closed the tab.
Just a heads up. And a Merry Christmas to everyone!