Enkira dies, triggering Nim Deathmantle, causing you to pay ({4} magic symbol) to return Enkira from your graveyard to the battlefield, and attach Nim Deathmantle to it.
Enkira enters the battlefield, creating two 2/2 Walker creature tokens.
Activate Ashnod's Altar by sacrificing a Walker, adding ({C} magic symbol) ({C} magic symbol) .