Activate Ashnod's Altar by sacrificing another nontoken creature, adding ({C} magic symbol) ({C} magic symbol) .
The creature dies, triggering Nim Deathmantle and Gutter Grime.
Resolve the Gutter Grime trigger, putting a slime counter on it and creating an X/X Ooze creature token.
Resolve the Nim Deathmantle trigger, causing you to pay ({4} magic symbol) to return the nontoken creature from your graveyard to the battlefield, and attach Nim Deathmantle to it.
Activate Ashnod's Altar by sacrificing the Ooze, adding ({C} magic symbol) ({C} magic symbol) .