When Infested Thrinax enters the battlefield, it triggers, causing you to create a number of 1/1 Saproling creature tokens when a nontoken creature you control dies.
Activate Thermopod's second ability by sacrificing Brokkos, adding ({R} magic symbol) .
When Brokkos dies, Infested Thrinax and Pitiless Plunderer trigger.
Resolve the Infested Thrinax trigger, creating six 1/1 Saproling creature tokens.
Resolve the Pitiless Plunderer trigger, creating a Treasure token.
Activate Thermopod's second ability twice by sacrificing two Saprolings, adding ({R} magic symbol) ({R} magic symbol) .
When the Saprolings die, Pitiless Plunderer triggers twice, creating two Treasure tokens.
Activate three Treasures by tapping and sacrificing them, adding ({UB} magic symbol) ({G} magic symbol) ({G} magic symbol) .
Cast Brokkos from your graveyard for its mutate cost by paying ({2} magic symbol) ({UB} magic symbol) ({G} magic symbol) ({G} magic symbol) , putting it on top of a Saproling.