Stone of Balance
3, tap: Choose a permanent card type (artifact, creature, land, enchantment, or planeswalker). If an opponent controls more of this permanent than you, destroy a permanent of the chosen type of your choice. This ability may only be played when you could cast a sorcery.
"Seems balanced" - Jace
Pure Nature cannot be countered.
If Pure Nature is sacrificed to a spell or ability from the opponent, instead exile it, then return it to the battlefield.
Pure Nature cannot have any counters of any type put on it.
If you did not cast Pure Nature, and it entered the battlefield, you lose the game.
Pure Nature may block any number of creatures.
Non-creature spells cannot be played.
Pure Nature cannot be tapped.
"Who plays blue and artifacts? Pfffft" -Elves in general.