Ghostly Prison

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

Nils, Discipline Enforcer

At the beginning of your end step, for each player, put a +1/+1 counter on up to one target creature that player controls.
Each creature with one or more counters on it can't attack you or planeswalkers you control unless its controller pays {X}, where X is the number of counters on that creature.

Horn of Gondor

When Horn of Gondor enters, create a 1/1 white Human Soldier creature token.
{3}, {T}: Create X 1/1 white Human Soldier creature tokens, where X is the number of Humans you control.

Sphere of Safety

Creatures can't attack you or planeswalkers you control unless their controller pays {X} for each of those creatures, where X is the number of enchantments you control.

Baird, Steward of Argive

Vigilance
Creatures can't attack you or planeswalkers you control unless their controller pays {1} for each of those creatures.

Templar Knight

Vigilance
{W}, Tap five untapped attacking creatures you control named Templar Knight: Search your library for a legendary artifact card, put it onto the battlefield, then shuffle.
A deck can have any number of cards named Templar Knight.

Archon of Absolution

Flying
Protection from white (This creature can't be blocked, targeted, dealt damage, enchanted, or equipped by anything white.)
Creatures can't attack you or planeswalkers you control unless their controller pays {1} for each of those creatures.

Norn's Annex

({W/P} can be paid with either {W} or 2 life.)
Creatures can't attack you or planeswalkers you control unless their controller pays {W/P} for each of those creatures.

The Circle of Loyalty

This spell costs {1} less to cast for each Knight you control.
Creatures you control get +1/+1.
Whenever you cast a legendary spell, create a 2/2 white Knight creature token with vigilance.
{3}{W}, {T}: Create a 2/2 white Knight creature token with vigilance.