Face-down creature spells you cast cost {1} less to cast.

Deathtouch Whenever a permanent you control is turned face up, you may return Deathmist Raptor from your graveyard to the battlefield face up or face down. Megamorph {4}{G} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)

Morph—Reveal a blue card in your hand. (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.) When Dragon's Eye Savants is turned face up, look at target opponent's hand.

Flying Morph {1}{G}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.) When Icefeather Aven is turned face up, you may return another target creature to its owner's hand.

As Ixidron enters the battlefield, turn all other nontoken creatures face down. (They're 2/2 creatures.) Ixidron's power and toughness are each equal to the number of face-down creatures on the battlefield.

When Kadena's Silencer is turned face up, counter all abilities your opponents control. Megamorph {1}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)

Morph {1}{G} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.) When Nantuko Vigilante is turned face up, destroy target artifact or enchantment.

Omarthis, Ghostfire Initiate enters the battlefield with X +1/+1 counters on it. Whenever you put one or more +1/+1 counters on another colorless creature, you may put a +1/+1 counter on Omarthis. When Omarthis dies, manifest a number of cards from the top of your library equal to the number of counters on it.

{T}: Add {C}. Spend this mana only to cast a face-down creature spell, pay a mana cost to turn a manifested creature face up, or pay a morph cost. (A megamorph cost is a morph cost.)

Flying Megamorph {1}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.) When Stratus Dancer is turned face up, counter target instant or sorcery spell.

As Vesuvan Shapeshifter enters the battlefield or is turned face up, you may choose another creature on the battlefield. If you do, until Vesuvan Shapeshifter is turned face down, it becomes a copy of that creature, except it has "At the beginning of your upkeep, you may turn this creature face down." Morph {1}{U}

At the beginning of your end step, manifest the top card of your library. (Put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.) Sacrifice Whisperwood Elemental: Until end of turn, face-up nontoken creatures you control gain "When this creature dies, manifest the top card of your library."

Morph {1}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.) When Willbender is turned face up, change the target of target spell or ability with a single target.

Face-down creature spells you cast cost {1} less to cast. {1}{G}: Turn Obscuring Aether face down. (It becomes a 2/2 creature.)

At the beginning of your end step, you may manifest the top card of your library. (Put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.) Exile a face-down permanent you control face up: You may play that card this turn. (You still pay its costs. Timing rules still apply.)

Face-down creatures you control get +0/+1. Whenever a permanent you control is turned face up, draw a card.

Whenever a face-down creature enters the battlefield under your control, you may search your library for a basic land card, reveal it, put it into your hand, then shuffle. Whenever a permanent you control is turned face up, if it's a creature, it gets +2/+2 until end of turn.