The problem is that its double X casting cost makes it harder to deal direct damage on larger scales
Furthermore, a weighted card, or one thats slightly bigger than the rest, could make it easier to pick out in cases where your opponent gives you a set of face-down cards to pick from
This Eldrazi rewards you whenever your colorless creatures die, building experience counters throughout the game
Conversely, with Chronomaton the problem was that youd invest a lot of time and mana into a creature, and then when you finally got around to trying to do something with it your opponent could just kill it and youd have nothing to show for it but Hangarback Walker is very much the opposite unless your opponent has just the right removal spell
You need to be brave if you want to sleeve up a promo copy though
The end of month rewards for attaining different ranks are as follows: Bronze: one pack