Activate Ashnod's Altar by sacrificing any nontoken creature, adding ({C} magic symbol) ({C} magic symbol) .
The creature dies, triggering Nim Deathmantle, causing you to pay ({4} magic symbol) to return the creature from your graveyard to the battlefield, and attach Nim Deathmantle to it.
The creature enters the battlefield, triggering Blessed Sanctuary, creating a 2/2 Unicorn artifact creature token.
Activate Ashnod's Altar by sacrificing the Unicorn, adding ({C} magic symbol) ({C} magic symbol) .