Back from the Doom

As an additional cost to cast this spell, pay an
amount of life equal to the number of cards in
your graveyard.
Each player mills a number of cards equal to half
your life total, rounded down. If this spell was
cast from your graveyard, each player returns all
creature cards from their graveyard to the battlefield tapped, except they're black Zombies.
Flashback {9}{b}{b}{b}{b}