Chthonian Nightmare | Priest of Gix | Skittering Precursor

(and one other card)

Activate
Altar of Dementia by sacrificing
Priest of Gix.
When
Priest of Gix dies,
Skittering Precursor triggers, creating a 0/1 Eldrazi Spawn creature token.
Resolve the
Altar of Dementia ability, causing target player to mill cards equal to
Priest of Gix's power.
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) .
Cast
Chthonian Nightmare by paying ({1} magic symbol) ({B} magic symbol) .
When
Chthonian Nightmare enters the battlefield, it triggers, causing you to get ({E} magic symbol) ({E} magic symbol) ({E} magic symbol) .
Repeat.