Azor I's Martial Decree

(You may cast a legendary sorcery only if you control
a legendary creature or planeswalker.)
Exile 3 permanents. For the rest of the game,
at the beginning of your upkeep, you may exile another permanent.
"Crimes against Ravnica will not go unpunished.
If the Guildpact is not strong enough, I will be."
-Azor I