Gateway from Death

Gateway From Death enters the battlefield
with a return counter on it if {b} was used to play it, and a fortune counter if {u} was used to play it.
When your life becomes 0, instead, sacrifice this artifact. Your life becomes your starting life total. If it has a return counter on it, return all creatures from your graveyard to the battlefield. If it has a fortune counter on it, shuffle your graveyard into your library.