This loop relies on an infinite recursion engine fueled by Technomancer's ability to pull back an artifact creature from the graveyard when it enters the battlefield. By having Phyrexian Metamorph enter as a copy of Technomancer, you trigger a fresh wave of milling and reanimation, allowing you to continually recycle your loop pieces. Krark-Clan Grunt serves as the vital outlet that lets you sacrifice the copying Metamorph in response to its own trigger, sending it safely back to the graveyard so the process can begin anew.