Activate Krark-Clan Ironworks by sacrificing Myr Battlesphere, adding CC.
When Myr Battlesphere dies, Nim Deathmantle triggers, causing you to pay 4 to return Myr Battlesphere from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Myr Battlesphere enters, it triggers, creating four artifact creature tokens.
Activate Krark-Clan Ironworks by sacrificing a creature token, adding CC.