Siphoning Madness

Amass 2. (Put two +1/+1 counters on an
Army you control. If you don't control one,
create a 0/0 black Zombie Army creature token first.)
Target player loses X life, puts the top X
cards of his or her library into his or her
graveyard and you gain X life, where X
is the greatest power among creatures you
control.