Ashnod's Altar by sacrificing a nontoken creature, adding ({C} magic symbol) ({C} magic symbol) .
When the creature dies,
Bridge from Below and
Nim Deathmantle triggers.
Resolve the
Bridge from Below trigger, creating a 2/2 Zombie creature token.
Activate
Ashnod's Altar by sacrificing the Zombie, adding ({C} magic symbol) ({C} magic symbol) .
Resolve the
Nim Deathmantle trigger from step 2, causing you to pay ({4} magic symbol) to return the nontoken creature from your graveyard to the battlefield, and attach