Oracle's Vault
Artifact
, 
: Exile the top card of your library. Until end of turn, you may play that card. Put a brick counter on Oracle's Vault.
: Exile the top card of your library. Until end of turn, you may play that card without paying its mana cost. Activate this ability only if there are three or more brick counters on Oracle's Vault.
Illustrated by
Amonkhet#234RareEnglishLegality
Rulings
The cards exiled by Oracle’s Vault are exiled face up.
You may play the exiled card this turn even if Oracle’s Vault is no longer on the battlefield or under your control.
Playing a card exiled with Oracle’s Vault follows the normal timing rules for playing that card. For example, if the card is a creature card, you can cast that card only during your main phase while the stack is empty.
If the exiled card is a land card, you may play it only if you have an available land play this turn.
If you don’t play the card, it will remain exiled.
The first ability of Oracle’s Vault puts a brick counter on it even if you can’t or don’t play the card.
If you cast a card “without paying its mana cost,” you can’t choose to cast it for any alternative costs, such as emerge costs. You can, however, pay additional costs. If the card has any mandatory additional costs, such as that of Tormenting Voice, those must be paid to cast the card.
If the card has X in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.