Jihad

As this enchantment enters, choose a color and an opponent.
White creatures get +2/+1 as long as the chosen player controls a nontoken permanent of the chosen color.
When the chosen player controls no nontoken permanents of the chosen color, sacrifice this enchantment.

Aragorn, King of Gondor

Vigilance, lifelink
When Aragorn enters, you become the monarch.
Whenever Aragorn attacks, up to one target creature can't block this turn. If you're the monarch, creatures can't block this turn.

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.