Icefeather Aven

You must ensure that your face-down spells and permanents can easily be differentiated from each other. You're not allowed to mix up the cards that represent them on the battlefield in order to confuse other players. The order they entered the battlefield should remain clear. Common methods for doing this include using markers or dice, or simply placing them in order on the battlefield.

When the spell resolves, it enters the battlefield as 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 creature can still grant it any of these characteristics.

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.

The face-down spell has no mana cost and has a mana value of 0. When you cast a face-down spell, put it on the stack face down so no other player knows what it is, and pay {3}. This is an alternative cost.

If a face-down permanent leaves the battlefield, you must reveal it. You must also reveal all face-down spells and permanents you control if you leave the game or if the game ends.

Morph lets you cast a card face down by paying {3}, and lets you turn the face-down permanent face up any time you have priority by paying its morph cost.