You have at least three other cards in your graveyard.
({2} magic symbol) ({B} magic symbol) available.
Steps
Cast Priest of Gix from your graveyard for its escape cost by paying ({2} magic symbol) ({B} magic symbol) and exiling three other cards from your graveyard.
Priest of Gix enters the battlefield, adding ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) .
Activate Lord of the Forsaken's first ability by paying ({B} magic symbol) and sacrificing Priest of Gix.
Priest of Gix dies, triggering Blood Artist, causing an opponent to lose 1 life and you to gain 1 life.
Resolve the Lord of the Forsaken ability, causing you to mill three cards.
Activate Lord of the Forsaken's second ability by paying 1 life, adding ({C} magic symbol) that can only be spent to cast spells from your graveyard.