Ricardo Silva If I am not mistaken, Yawgmoth, Thran Physician is the only four mana creature being played in Modern which has no enters the battlefield effect
Trap cards have fallen the furthest, with many decks using only the bare minimum, due to the setup time required
Riverchurn Monument is the kind of mill card that scares me, because it tends to combo with a bunch of mill favorites like Bruvac, Phenax, God of Deception, and ways to make players mill a lot of cards (Maddening Cacophony, anyone?)
You cannot declare attacks the turn you activate this effect, except with Xyz Monsters
As the last chapter ability resolves, you may choose to exile all other creatures even if you didn't choose any Doctors