When Edgewall Pack dies, Nim Deathmantle triggers, causing you to pay ({4} magic symbol) to return Edgewall Pack from your graveyard to the battlefield, and attach Nim Deathmantle to it.
When Edgewall Pack enters the battlefield, it triggers, creating a 1/1 Rat creature token.
Activate Ashnod's Altar by sacrificing the Rat, adding ({C} magic symbol) ({C} magic symbol) .