Activate Ashnod's Altar by sacrificing Ministrant of Obligation, adding ({C} magic symbol) ({C} magic symbol) .
When Ministrant of Obligation dies, its afterlife ability and Nim Deathmantle trigger.
Resolve the Ministrant of Obligation trigger, creating two 1/1 Spirit creature tokens.
Activate Ashnod's Altar by sacrificing a Spirit, adding ({C} magic symbol) ({C} magic symbol) .
Resolve the Nim Deathmantle trigger from step 2, causing you to pay ({4} magic symbol) to return Ministrant of Obligation from your graveyard to the battlefield, and attach Nim Deathmantle to it.