Activate Ashnod's Altar by sacrificing Patron of the Arts, adding ({C} magic symbol) ({C} magic symbol) .
Patron of the Arts dies, triggering itself and Nim Deathmantle.
Resolve the Patron of the Arts trigger, creating a Treasure token.
Activate the Treasure token by tapping and sacrificing it, adding ({1} magic symbol) .
Resolve the Nim Deathmantle trigger, causing you to pay ({4} magic symbol) to return Patron of the Arts from your graveyard to the battlefield, and attach Nim Deathmantle to it.
Patron of the Arts enters the battlefield, creating a Treasure token.
Activate the Treasure token by tapping and sacrificing it, adding ({1} magic symbol) .