Activate Ashnod's Altar by sacrificing Angel of Invention, adding ({C} magic symbol) ({C} magic symbol) .
Angel of Invention dies, triggering Nim Deathmantle, causing you to pay ({4} magic symbol) to return Angel of Invention from your graveyard to the battlefield, and attach Nim Deathmantle to it.
Angel of Invention enters the battlefield, creating two 1/1 Servo creature tokens.
Activate Ashnod's Altar by sacrificing a Servo, adding ({C} magic symbol) ({C} magic symbol) .