{Farseek} how does this work?
{Farseek} allows you to search your library for a land that is a {Plains}, {Mountain}, {Island}, or a {Swamp} in its card type, and put that land on the battlefield tapped. It's a little different from most land searches, because it doesn't let you search for any basic land - you can't use it to search for a {Forest}.
Mostly, this card is used in combination with the Ravnica "Shock Lands," like {Temple Garden}, {Watery Grave}, {Sacred Foundry}, and so on. Because these special lands have the basic land types printed on them ({Watery Grave is a 'Land - Swamp Island,' whereas {Drowned Catacomb} is simply just 'Land,' for example), Farseek is able to search for them.
RESOLVED