Reidane, God of the Worthy will tax any opponent wanting to cast a noncreature spell with a CMC of four or more
Though it lacks the tax effect of Rhystic Study, Fairy Mastermind draws you into the game quietly and steadily
This is why it can be tricky trying to predict the values of cards before a set is out in the wild, as you never know which cards will get pulled into relevance
It's time for another mono-colored commander deck
There are tons of ways to get counters on creatures so Volrath can turn into them, but my favorite is Tetzimoc, Primal Death, which can repeatedly put a prey counter on any creature for just one black mana
The game checks through a list of these rules any time a player is about to get priority, and uses state-based actions to move cards around and otherwise ensure those rules are enforced correctly