Wildcall

If you choose 0 for X, you'll just manifest the top card of your library.

There are no cards in the Fate Reforged set that would turn a face-down instant or sorcery card on the battlefield face up, but some older cards can try to do this. If something tries to turn a face-down instant or sorcery card on the battlefield face up, reveal that card to show all players it's an instant or sorcery card. The permanent remains on the battlefield face down. Abilities that trigger when a permanent turns face up won't trigger, because even though you revealed the card, it never turned face up.

At any time, you can look at a face-down permanent you control. You can't look at face-down permanents you don't control unless an effect allows you to or instructs you to.

Turning a permanent face up or face down doesn't change whether that permanent is tapped or untapped.

The face-down permanent is a 2/2 creature with no name, mana cost, creature types, or abilities. It's colorless and has a mana value of 0. Other effects that apply to the permanent can still grant or change any of these characteristics.

Any time you have priority, you may turn a manifested creature face up by revealing that it's a creature card (ignoring any copy effects or type-changing effects that might be applying to it) and paying its mana cost. This is a special action. It doesn't use the stack and can't be responded to.

A permanent that turns face up or face down changes characteristics but is otherwise the same permanent. Spells and abilities that were targeting that permanent, as well as Auras and Equipment that were attached to the permanent, aren't affected.

If a double-faced card is manifested, it will be put onto the battlefield face down. While face down, it can't transform. If the front face of the card is a creature card, you can turn it face up by paying its mana cost. If you do, its front face will be up.

If a manifested creature would have morph if it were face up, you may also turn it face up by paying its morph cost.

Because the permanent is on the battlefield both before and after it's turned face up, turning a permanent face up doesn't cause any enters-the-battlefield abilities to trigger.