Wurmcoil Engine dies, triggering itself and Nim Deathmantle.
Resolve the Wurmcoil Engine triggers, creating a 3/3 Wurm token with deathtouch and a 3/3 Wurm token with lifelink.
Holding priority, activate Ashnod's Altar by sacrificing one of the Wurm token, adding ({C} magic symbol) ({C} magic symbol) .
Resolve the Nim Deathmantle triggers, causing you to pay ({4} magic symbol) to return Wurmcoil Engine from your graveyard to the battlefield, and attach Nim Deathmantle to it.