When Eyeblight Cullers dies, it and Nim Deathmantle triggers.
Resolve the Eyeblight Cullers trigger, creating three 1/1 Elf Warrior creature tokens.
Activate Ashnod's Altar by sacrificing an Elf Warrior, adding ({C} magic symbol) ({C} magic symbol) .
Resolve the Nim Deathmantle trigger from step 2, causing you to pay ({4} magic symbol) to return Eyeblight Cullers from your graveyard to the battlefield, and attach Nim Deathmantle to it.