Vizier of the Menagerie

Vizier of the Menagerie lets you look at the top card of your library whenever you want (with one restriction—see below), even if you don't have priority. This action doesn't use the stack. Knowing what that card is becomes part of the information you have access to, just like you can look at the cards in your hand.

Normally, Vizier of the Menagerie allows you to cast the top card of your library if it's a creature card, it's your main phase, and the stack is empty. If that creature card has flash, you'll be able to cast it any time you could cast an instant, even on an opponent's turn.

The top card of your library isn't in your hand, so you can't cycle it, discard it, or activate any of its activated abilities.