Safe of Eternity

When Safe of Eternity enters the battlefield, search your library for a card and exile it face down with four time counters on it.
At the beginning of your upkeep, remove a time counter from the exiled card. When the last is removed, place the exiled card in your hand and place Safe of Eternity on the top of your library, then shuffle your library.
Only open it, if you're ready to embrace the power.