Sacred Woods

Infuse {g}{g} (When this land enters the battlefield,
you may pay {g}{g}. If you do, it becomes infused.)
{t}: Add {g}.
The first time a nontoken nonartifact creature
enters the battlefield under your control each
turn, if Sacred Woods is infused, untap it.
There's a magic in the old forests of the world, with the
glow of enchantment rife in the air.