Activate Ashnod's Altar by sacrificing Patagia Viper, adding CC.
When Patagia Viper dies, Nim Deathmantle triggers, causing you to pay 4 to return Patagia Viper from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Patagia Viper enters, it triggers twice.
Resolve the first trigger, creating two creature tokens.
Holding priority, activate Ashnod's Altar twice by sacrificing Patagia Viper and a creature token, adding CCCC