Teriel, Earth Incarnate

When Teriel, Earth Incarnate enters the battlefield, exile all your lands, then search your library for four lands, exile them, and shuffle your library. Whenever you play a land, exile it. You may tap exiled lands. If an exiled land were to add mana to your mana pool, it adds twice that much mana instead. When Teriel, Earth Incarnate dies, return all your exiled lands. They become 3/3 green elemental creature tokens in addition to their other types. They're still lands.