Rivendell, House of Elrond

Rivendell, House of Elrond enters the battlefield
tapped.
Whenever a nontoken Elf enters the battlefield
under your control, untap Rivendell, House
of Elrond.
{t}: Add {w} or {g} to your mana pool.
{1}, {t}: Add {w}{g} to your mana pool.