Seven Seals
The vision of the Seven Seals is a vision given to John the Divine in the Book of Revelation, chapter 6. It follows on from chapter 5, where John sees a Lamb (representing Jesus) holding a book with seven seals on it.
As the Lamb opens four of the seals, out come the Four Horsemen of the Apocalypse. When the fifth seal is broken, John sees a vision of the Christian martyrs. When the sixth seal is broken, destruction reigns on the earth and causes immense suffering. When the seventh seal is broken a few chapters later, we are told there was a "silence in heaven".