Playtest Cards: These are what WoTC designers use to test cards before they make it to the printing press
Like all great ideas, though, this one was only truly proven in the execution
2009-05-01 After youre done exiling cards and casting the last one if you chose to do so, the remaining exiled cards are randomly placed on the bottom of your library
Similar to Drown in the Loch, Witchs Vengeance is a card that might get unfairly typecast at first glance before taking time to consider its true strength
Second, they're less reliable because they're easier for your opponent to kill
For example, if one of the exiled cards is a land card, you may play it only during your main phase while the stack is empty and only if you have an available land play remaining