You have at least ({E} magic symbol) ({E} magic symbol) ({E} magic symbol) .
Steps
Activate Thermopod's second ability by sacrificing Priest of Gix, adding ({R} magic symbol) .
When Priest of Gix dies, Skittering Precursor triggers, creating a 0/1 Eldrazi Spawn creature token.
Activate Chthonian Nightmare by paying ({E} magic symbol) ({E} magic symbol) ({E} magic symbol) , sacrificing the Eldrazi Spawn and returning Chthonian Nightmare from the battlefield to your hand, returning Priest of Gix from your graveyard to the battlefield.
When Priest of Gix enters the battlefield, it triggers, adding ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) .