Revelation 6:8-10 New English Translation (NET Bible)
8 So I looked and here came a pale green horse! The name of the one who rode it was Death, and Hades followed right behind. They were given authority over a fourth of the earth, to kill its population with the sword, famine, and disease, and by the wild animals of the earth.
9 Now when the Lamb opened the fifth seal, I saw under the altar the souls of those who had been violently killed because of the word of God and because of the testimony they had given. 10 They cried out with a loud voice, “How long, Sovereign Master, holy and true, before you judge those who live on the earth and avenge our blood?”