Activate Ashnod's Altar by sacrificing a nontoken artifact creature, adding CC.
The creature dies, triggering Nim Deathmantle, causing you to pay 4 to return the artifact creature from your graveyard to the battlefield, and attach Nim Deathmantle to it.
Imotekh's first ability triggers, creating two 2/2 Necron Warrior artifact creature tokens.
Activate Ashnod's Altar by sacrificing a Necron Warrior, adding CC.