You have at least ({E} magic symbol) ({E} magic symbol) ({E} magic symbol) .
Steps
Activate Ashnod's Altar by sacrificing Priest of Gix, adding ({C} magic symbol) ({C} magic symbol) .
When Priest of Gix dies, Fumulus's first ability triggers, creating a 1/1 Insect creature token.
Activate Chthonian Nightmare by paying ({E} magic symbol) ({E} magic symbol) ({E} magic symbol) , sacrificing the Insect 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) .