That would trigger his TIMELY ALLIANCE ability to look at the top card of your deck
As such Mystic Confluence is generally on par with the cube power level of cost to return (assuming you don't have to repeatedly Mana Leak the same target)
This is a way to sneak in creatures to attack that arent even in play yet and take advantage of excellent abilities that only trigger when the creature deals combat damage to a player
First of all, the swap happens as Deadpool enters, not when it enters, which means the ability doesnt go on the stack for your opponent to respond to
Players will get a rare illustrated version of either legendary in the Elite Trainer Box, alongside several booster packs, energy cards, sleeves, coins, damage tokens and dice
We've got loads of cards spiking thanks to the ludicrous Discover keyword, as well as Merfolk that can counter Cascade, and a possible Discover hate card that's done nothing to stop the rampage of this new ability keyword