Erosion

Enchant land
At the beginning of the upkeep of enchanted land's controller, destroy that land unless that player pays {1} or 1 life.

Rhystic Tutor

Unless any player pays {2}, search your library for a card, put that card into your hand, then shuffle.

Propaganda

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

Flay

Target player discards a card at random. Then that player discards another card at random unless they pay {1}.

Seizures

Enchant creature
Whenever enchanted creature becomes tapped, Seizures deals 3 damage to that creature's controller unless that player pays {3}.

Lim-Dûl's Hex

At the beginning of your upkeep, for each player, Lim-Dûl's Hex deals 1 damage to that player unless they pay {B} or {3}.

Aether Barrier

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

Rhystic Deluge

{U}: Tap target creature unless its controller pays {1}.

Power Sink

Counter target spell unless its controller pays {X}. If that player doesn't, they tap all lands with mana abilities they control and lose all unspent mana.

Arboria

Creatures can't attack a player unless that player cast a spell or put a nontoken permanent onto the battlefield during their last turn.

Nether Void

Whenever a player casts a spell, counter it unless that player pays {3}.

Soul Barrier

Whenever an opponent casts a creature spell, Soul Barrier deals 2 damage to that player unless they pay {2}.

Mystic Remora

Cumulative upkeep {1} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Whenever an opponent casts a noncreature spell, you may draw a card unless that player pays {4}.

Isolation Cell

Whenever an opponent casts a creature spell, that player loses 2 life unless they pay {2}.

Slow Motion

Enchant creature
At the beginning of the upkeep of enchanted creature's controller, that player sacrifices that creature unless they pay {2}.
When Slow Motion is put into a graveyard from the battlefield, return Slow Motion to its owner's hand.

Cephalid Shrine

Whenever a player casts a spell, counter that spell unless that player pays {X}, where X is the number of cards in all graveyards with the same name as the spell.

Soul Tithe

Enchant nonland permanent
At the beginning of the upkeep of enchanted permanent's controller, that player sacrifices it unless they pay {X}, where X is its mana value.

Ghostly Prison

Invoke Prejudice

Whenever an opponent casts a creature spell that doesn't share a color with a creature you control, counter that spell unless that player pays {X}, where X is its mana value.

In the Eye of Chaos

Whenever a player casts an instant spell, counter it unless that player pays {X}, where X is its mana value.

Power Taint

Enchant enchantment
At the beginning of the upkeep of enchanted enchantment's controller, that player loses 2 life unless they pay {2}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Spelltithe Enforcer

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

Cleansing

For each land, destroy that land unless any player pays 1 life.

Rhystic Study

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