The mana value of the creature you find must be exactly equal to the number of age counters on Hibernation's End.
Cumulative upkeep (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Whenever you pay this enchantment's cumulative upkeep, you may search your library for a creature card with mana value equal to the number of age counters on this enchantment, put it onto the battlefield, then shuffle.
(At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)