1930 - an ancient vampire known as the Master tried to open the Hellmouth; however his attempts failed when an earthquake buried the abandoned church he had been living in, trapping him in there.

1997 - the Master's followers tried to free him and open the Hellmouth on two occasions. The first time, on the day know as The Harvest, the Master attempted to escape by using his minions as conduits to him, using the blood of their victims to give him the strength he needed to break out. The Slayer managed to stop his minions before they gave him back his full strength.