Activate Ashnod's Altar by sacrificing Slimefoot and Squee, adding ({C} magic symbol) ({C} magic symbol) .
Slimefoot and Squee dies, triggering Nim Deathmantle, causing you to pay ({4} magic symbol) to return Slimefoot and Squee from your graveyard to the battlefield, and attach Nim Deathmantle to it.
Slimefoot and Squee enters the battlefield, creating a 1/1 Saproling creature token.
Activate Ashnod's Altar by sacrificing the Saproling, adding ({C} magic symbol) ({C} magic symbol) .