Grand Arbiter Augustin IV

White spells you cast cost {1} less to cast.
Blue spells you cast cost {1} less to cast.
Spells your opponents cast cost {1} more to cast.

Windborn Muse

Flying
Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Spelltithe Enforcer

Whenever an opponent casts a spell, that player sacrifices a permanent of their choice unless they pay {1}.

Ghostly Prison

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Aura of Silence

Artifact and enchantment spells your opponents cast cost {2} more to cast.
Sacrifice Aura of Silence: Destroy target artifact or enchantment.

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Propaganda

Smothering Tithe

Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Dovin, Hand of Control

Artifact, instant, and sorcery spells your opponents cast cost {1} more to cast.
−1: Until your next turn, prevent all damage that would be dealt to and dealt by target permanent an opponent controls.