Act II: Gorgon Reference

When Macduff says, "Approach the chamber and destroy your sight/ With a new Gorgon.." he's relating to Greek mythology. The Gorgons are three sisters, who were very beautiful. Medusa, one of the sisters was the youngest and the most beautiful out of the three. She was turned into a monster with snakes as her hair, fangs, claws, and a black tongue. 

He said that 'With a new Gorgon' .. because Medusa was so horrible looking that everyone who looked at her, turned to stone. He meant that go into the bedroom to see what happened, and you'll freeze with horror to see what is there.