Kel'Thuzad, the Archlich

Creatures you control have Undying and Wither.
At the beginning of your end step, draw X cards,
where X is the number of -1/-1 counters on creatures on the battlefield.
At the beginning of your end step, gain X life
and all opponents lose X life, where X is the
number of creatures you control with a +1/+1
counter on it.