Revelation 6:7-9

New International Version - UK

⁷ When the Lamb opened the fourth seal, I heard the voice of the fourth living creature say, ‘Come!’ ⁸ I looked, and there before me was a pale horse! Its rider was named Death, and Hades was following close behind him. They were given power over a quarter of the earth to kill by sword, famine and plague, and by the wild beasts of the earth.

⁹ When he opened the fifth seal, I saw under the altar the souls of those who had been slain because of the word of God and the testimony they had maintained.