I have three scenarios, each involving a Misthollow Griffin exiled face down. In each case, the question is whether or not I can cast it from exile.

I control a Shared Fate and own a Misthollow Griffin exiled face down underneath it by my opponent. The rules don't allow me to look at it, but I know it's there because the top of my library was revealed by Oracle of Mul Daya at the time it was exiled.

I control a Shared Fate and own a Misthollow Griffin exiled face down underneath it by my opponent. The rules do allow me to look at it, because Mindslaver's effect let me control my opponent's last turn, and I was able to look at it then.

I control a Bane Alley Broker and own a Misthollow Griffin exiled face down underneath it.

We actually have a rule that covers these situations:

406.3. Exiled cards are, by default, kept face up and may be examined by any player at any time. Cards “exiled face down” can’t be examined by any player except when instructions allow it. However, once a player is allowed to look at a card exiled face down, that player may continue to look at that card as long as it remains exiled, even if the instruction allowing the player to do so no longer applies. A card exiled face down has no characteristics, but the spell or ability that exiled it may allow it to be played from exile. Unless that card is being cast face down (see rule 707.4), the card is turned face up just before the player announces that he or she is playing the card (see rule 601.2).

The relevant section is “A card exiled face down has no characteristics”, so while you (the player) may know what the card is, the game does not, since it's face down and has no characteristics. So you would not be able to cast the Griffin in any of those situations, since it does not have the ability that lets you cast it while it's face down.

Nathan Long
Wizards.Com Boards NetRep