Revival
Sorcery
Return target creature card with mana value 3 or less from your graveyard to the battlefield.
Illustrated by
Ravnica Remastered#241RareEnglishLegality
Rulings
Jan 25, 2019
If a card in a graveyard has 
in its mana cost, X is considered to be 0.
Jan 25, 2019
To double a player’s life total, that player gains as much life as needed so that their life total is twice the number it was before. If their life total was negative, that player loses as much life as needed so that their life total is twice as far below 0 as it was before. Other effects interact with this life gain or loss accordingly.