If they deal damage through an attack, and even if they knock out Iron Boulder ex, you get to put eight damage counters on the Pokemon that damages it
This card was spoiled later in the Livestream and appears in the Commander section of this article
W for a 1/1 (So far, so good.) 2W for a 2/2 (Pearled Unicorn, but not horrible.) 10W for a 5/5 first strike creature (Wait, what?) 1U for a 0/3 (Eh, but bearable.) 3U for a 0/6 (Getting pretty bad here.) 11U for a 6/6 islandwalk creature (Wait, what?) B for a 1/1 (Muck Rats, but okay.) 4B for a 3/3 (Looking a little worse here.) 12B for a 5/5 creature with pseudo-fear (Wait, what?) Those ultimate mana costs were paid out over multiple turns, but if your creature died before hitting their highest level game over, tons of wasted mana, yikes
2x2, 2x3, 2x4, 3x3, 3x4, 3x10, etc