Curious card, it's these kinda mechanics that change the game considerably. That said, it relies on the player swarming the field or using adrenaline before hand, but when utilized properly, can probably be almost as dangerous as a Ruby dragon or Diving Wyrm.
let's see how this rolls. Ash eaters cost 1
and if it's the third or fourth creature spawned, it basically gets +1/0 for every creature that attacks before it. And that's without buffs.
Adrenaline adds anywhere from +3/0 to +5/0 to this thing, while simutaniously boosting another creatures attack by at least *2, if not more.
So with a few creatures placed before it, it winds up something like 7/2, with adrenaline, it becomes at least 10/2 and that's if you use only 1 adrenaline.
So might need a cost buff, but it's hard to balance 'strategy' cards like this one who's powers are based on how well they are applied.