Ritual de nacimiento

Birthing Ritual's ability checks if you control a creature at the beginning of your end step. If you don't, the ability won't trigger.

If Birthing Ritual's ability does trigger but you control no creatures when it tries to resolve, the ability will do nothing.

If one of the revealed creature cards has {X} in its mana cost, X is 0 when determining that card's mana value.

Use the mana value of the sacrificed creature as it last existed on the battlefield to determine the value of X.