Dol Guldur

Dol Guldur enters the battlefield tapped.
{t}: Add {b}, {r}, or {g} to your mana pool.
{x}{b}{r}{g}, {t}, Sacrifice another land: Target creature gets +X/+X until end of turn.
"I dared pass the doors of Dol Guldur, the stronghold of the Enemy in the North..."