Ravnica common. In a world like Ravnica, mana fixing is obviously crucial. The challenge for the design team with this one was that they wanted a card which could take advantage of the new dual lands, but which didn’t strictly obsolete Rampant Growth. To accomplish both, Farseek was worded to get any land type other than forest, but note that it can still search out any of the new dual lands that is also a Forest.
