Volrath's Firstborn

At the beginning of your upkeep, put a parasite
counter on target creature, then put a -1/-1
counter on each creature with a parasite counter.
Whenever a creature dies, if it had a parasite
counter on it, draw cards and lose life equal to
the number of -1/-1 counters on it.
{t}, Discard X cards: Gain control of target
creature with mana value X that has a
parasite counter on it.