Breakneck, Slaughter-Bot

Whenever Breakneck, Slaughter-Bot attacks, defending player sacrifices an artifact.
Whenever an artifact card is put into a graveyard
from anywhere, Breakneck, Slaughter-Bot deals 2 damage to any target.
Breakneck, Slaughter-Bot's power is equal to the
total number of artifact cards in graveyards.
C r o n c h.