Savior of the Small

If a creature's survival ability triggers but that creature is untapped when the ability begins to resolve, that ability won't do anything.

If the mana cost of a card in your graveyard includes {X}, X is 0 for the purpose of determining its mana value.

Survival abilities (and other abilities that trigger at the beginning of your second main phase) will trigger at the beginning of the second main phase you take in a turn. They won't trigger during your third, fourth, or other additional main phases in a single turn, if effects somehow cause you to have more than two main phases.