The Parasite Blade

Equip Planeswalker {2}{p/b}{p/b}
Equip {2}{p/b}{p/b}
The Parasite Blade's equip ability costs {2} less to activate if it targets a Sorin planeswalker.
Whenever equipped creature or planeswalker deals or receives damage to/from a nonartifact creature, that creatures controller sacrifices it. Whenever a creature is sacrificed this way put X +1/+1 counters or loyalty counters on equipped creature or planeswalker where X is half of the sacrificed creature's CMC rounded down.