Activate Ashnod's Altar by sacrificing any nontoken creature, adding ({C} magic symbol) ({C} magic symbol) .
The creature dies, triggering Nim Deathmantle, causing you to pay ({4} magic symbol) to return the creature from your graveyard to the battlefield, and attach Nim Deathmantle to it.
The creature enters the battlefield, triggering Genesis Chamber, creating a 1/1 Myr artifact creature token.
Activate Ashnod's Altar by sacrificing the Myr, adding ({C} magic symbol) ({C} magic symbol) .