If the creature you put onto the battlefield leaves the battlefield before damage is dealt, its last known existence on the battlefield is used to determine how much damage it deals to the target creature.

You don’t choose any targets as you cast Vivien’s Invocation. While that spell is resolving, you may put a creature card from among the cards you look at onto the battlefield. If you do, a separate ability triggers and you pick a target creature an opponent controls to be dealt damage.