Nim Deathmantle and Ashnod's Altar on the battlefield.
You control at least one nontoken creature.
Steps
Activate 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 Nim Deathmantle to it.