Are cards exiled with Ashiok revealed?
Comprehensive rules:


  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).