Activate Ashnod's Altar by sacrificing Sling-Gang Lieutenant, adding CC.
When Sling-Gang Lieutenant dies, Nim Deathmantle triggers, causing you to pay 4 to return Sling-Gang Lieutenant from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Sling-Gang Lieutenant enters, it triggers, creating two creature tokens.
Activate Ashnod's Altar by sacrificing a creature token, adding CC.