When Liberated Livestock dies, it and Nim Deathmantle triggers.
Resolve the Liberated Livestock trigger, creating a 1/1 Cat, a 1/1 Bird, and a 2/4 Ox creature token.
Activate Ashnod's Altar by sacrificing a creature token, adding ({C} magic symbol) ({C} magic symbol) .
Resolve the Nim Deathmantle trigger from step 2, causing you to pay ({4} magic symbol) to return Liberated Livestock from your graveyard to the battlefield, and attach Nim Deathmantle to it.