Muriel, Divine Truth

Whenever a player taps a land for mana, that player adds one mana of any type that land produced.

Whenever an opponent casts a creature spell, you
may look at the top card of your library. If it's a creature card, you may reveal it. If you do, you may cast it without paying its mana cost if the two creatures share the same power and/or toughness. Otherwise, you may put it on the bottom of your library.