While most of the game's attacks are guaranteed to be at least moderately successful, some of them have a bit of a luck factor to them, and flipping a coin is occasionally required for a card
Since Invasion' s creature wars usually began on turn two, you could drop a turn two bear, and then hold back Exclude for anything your opponent might drop
By the same token, however, WotC inherently takes a risk whenever they work on a new product that it may, through some channel or another, make its way to the public before its intended announcement date
It can be any card so long as it has the golden circle shown above around its Ink Cost
If you like tricky decks with a lot of card interactions and combos, I would definitely recommend this deck
Add in that Ephara is indestructible, and it becomes very difficult to stop this deck once it really gets going