11 Unown There are actually two Unown cards banned from expanded play, both of which belong to the Sun & Moon - Lost Thunder set
Four Knocks is like a white Phyrexian Arena for a couple turns, and you can blink it to make it last longer or retrieve it with Sun Titan effects
I cant recommend it, and Im not even willing to say its a cool design
Returning all nonland permanents you don't control to its owner's hand, is probably one of the biggest, most powerful things you can do at Instant speed
It takes little effort to get multiple landfall triggers, so this takes over games in no time
But the really revolutionary thing is to have your permanents already in play help you pay to add more of them, leading to exponential or even infinite board-widening in a single turn