Activate Thermopod's second ability by sacrificing Nevinyrral, adding ({R} magic symbol) .
When Nevinyrral dies, its second ability and Nim Deathmantle trigger.
Resolve the Nevinyrral trigger, choosing not to pay.
Resolve the Nim Deathmantle trigger, causing you to pay ({4} magic symbol) to return Nevinyrral to the battlefield from your graveyard, and attach Nim Deathmantle to it.
When Nevinyrral enters the battlefield, its first ability triggers, creating a tapped 2/2 Zombie creature token for each creature that has died this turn.
Activate Thermopod's second ability three times by sacrificing three Zombie tokens, adding ({R} magic symbol) ({R} magic symbol) ({R} magic symbol) .