Matice Vaazi, the Collector

Metalcraft - Matice Vaazi, the Collector cannot
attack unless you control three or more artifacts.
Rive (While a creature with Rive is on the battlefield, whenever an artifact is put into the
graveyard from the battlefield you mill a card.)
When Matice Vaazi, the Collector enters the battlefield or attacks you may return an artifact
from your graveyard to your hand.