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 Hibernation’s End’s cumulative upkeep, you may search your library for a creature card with converted mana cost equal to the number of age counters on Hibernation’s End and put it onto the battlefield. If you do, shuffle your library.