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