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