Parasite, Life Draining Sword

Equipped creature gains +4/+4.
Whenever equipped creature deals combat
damage to a player, sacrifice it. Search your
library for a creature with CMC equal to or less
than the damage dealt by the sacrificed creature.
Reveal it, then you may pay {b}{b}{g}{g} and
4 life. if you do, put the creature into the
battlefield tapped and attach this card to it. If you
don't, add it to your hand. Shuffle you library.
Equip: {1}{p/b}{p/g}
Parasite can be your commander.