Urgrem, Labyrinth Keeper

When Urgrem, Labyrinth Keeper enters the battlefield, you may sacrifice a land. If you do, search your library for a land named Labyrinth of Skophos and put it onto the battlefield. Then shuffle your library.
Activated abilities of Minotaurs and nonbasic lands you control that aren't mana abilities cost {4} less to activate. This effect can't reduce the mana in that cost to less than one mana.