Only 110 cards were printed, so what could be more expensive than that
Rather than stuffing the deck with random Commander staples, Wizards appears to have chosen reprints that actively reinforce what Avengers Assemble is trying to do even if some players only buy the new precon to strip it for parts.
I think there are ways to efficiently increase the chances of having a storm count (Nykthos, Shrine to Nyx to generate a ton of mana the turn we want to resolve this, for instance), but since this deck is meant for beginners, Im going to keep the mana base simple
Once per turn, "Dark Realm" monsters cannot be destroyed by battle or card effects
The card has diminishing returns, and its totally fine to play one, two, or three copies, if needed