Drawing down, outside of poker, refers to when someone draws their firearm with intent to use it. The intent is to solve the problem with deadly force, or at least let the suspect know that they are about to be solved with deadly force. In poker, drawing down serves the same purpose, but there isn't a gun involved. You also don't draw.
Necromancy, the art of raising the dead is often a subject best left for horror films and reprints of the Necronomicon. However, necromancy also finds a place in discussing poker, not because there is a strong trend of zombies playing poker, but because of the way a poker game often seems to be its own form of necromancy.