Unearth
Sorcery
Return target creature card with mana value 3 or less from your graveyard to the battlefield.
Cycling 
No matter how deep you bury it, some evil refuses to stay dead.
Jehan Choo
Rulings
If a card in a player's graveyard has {X} in its mana cost, X is considered to be 0.
(wotc • 2019-06-14)
Rulings
If a card in a player's graveyard has {X} in its mana cost, X is considered to be 0.
(wotc • 2019-06-14)