You control a nonlegendary, nontoken creature that has a creature type chosen with Molten Echoes.
({2} magic symbol) available.
Steps
Activate Ashnod's Altar by sacrificing a nonlegendary, nontoken creature with a creature type named by Molten Echoes, adding ({C} magic symbol) ({C} magic symbol) .
Nim Deathmantle triggers, 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 Molten Echoes, creating a token copy of that creature with haste.
Activate Ashnod's Altar by sacrificing the token, adding ({C} magic symbol) ({C} magic symbol) .