You control at least one nontoken artifact creature.
({2} magic symbol) available.
Steps
Activate Krark-Clan Ironworks by sacrificing a nontoken artifact creature, adding ({C} magic symbol) ({C} magic symbol) .
When the creature dies, Nim Deathmantle triggers, causing you to pay ({4} magic symbol) to return the creature from your graveyard to the battlefield, and attach Nim Deathmantle to it.
When the creature enters the battlefield, its fabricate ability triggers, creating a 1/1 Servo artifact creature token.
Activate Krark-Clan Ironworks by sacrificing the Servo, adding ({C} magic symbol) ({C} magic symbol) .