The card spoiled in his article is Dezimierer der Provinzen, or in English, Decimator of the Provinces (credit for card translation goes to reddit user RedEchoGamer)
Gyarados is the bane of my existence, the last piece for my collections
Its monocolor, instant speed, gets you back any previously-milled threat, and has some pretty significant interactions with other powerful spells including the number one self-mill effect on our list 1
Since none of them made it to the market, the estimated worth of a single card is $10,000+
During your Draw Phase, if this card is in your GY, before you draw: You can give up your normal draw this turn, and if you do, add this card to your hand
If you're Boros and you goad three of an opponent's creatures, reward yourself with a card, then it comes back to your turn and you send in the battallion, and you draw more