If an exiled card has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.

Casting the exiled card follows the normal timing rules for casting 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 you cast a card “without paying its mana cost,” you can’t pay any alternative costs. You can, however, pay additional costs. If the card has any mandatory additional costs, such as that of Silvergill Adept, those must be paid to cast the card.

If a token is exiled this way, it can’t be cast.