Realm of the Dead

Syphon (You may pay any amount of life as you
cast this spell, this spell costs {x} less to cast where X
is the amount of life spent.)
When you cast Realm of the Dead, if it was not
copied, any number of players may cast a copy of
it and may spend mana as though it were mana
of any color to cast the copy.
Return target creature card with mana value X or
less from your graveyard to the battlefield.