Dominaria United: Karn's Sylex
Karn's Sylex enters the battlefield tapped.
Player's can't pay life to cast spells or to activate abilities that aren't mana abilities.
, , Exile Karn's Sylex: Destroy each nonland permanent with mana value X or less. Activate only as a sorcery.
A threatening board wipe that you can play preemptively, having one of these on the battlefield will make your opponents have to choose very carefully how to proceed. Being able to selectively destroy only smaller things can easily be worked to your advantage.