Unmarked Graves

Whenever a card would be put into a graveyard that card is put there face down (No players see it, it remains face down until it leaves the graveyard).
If a spell or ability would make a card leave a graveyard, that card makes a card at random from that graveyard leave that graveyard in that way (If the card that would leave the graveyard doesn't share a card type that would allow it to leave the graveyard because of