Activate Ashnod's Altar by sacrificing another nontoken creature, adding ({C} magic symbol) ({C} magic symbol) .
When the creature dies, Golgari Germination and Nim Deathmantle trigger.
Resolve the Golgari Germination trigger, creating a 1/1 Saproling creature token.
Activate Ashnod's Altar by sacrificing the Saproling, 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 sacrificed creature from your graveyard to the battlefield, and attach Nim Deathmantle to it.