Revelation 6:9

6:9 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.

Revelation 8:5

8:5 Then the angel took the censer, filled it with fire from the altar, and threw it on the earth, and there were crashes of thunder, roaring, flashes of lightning, and an earthquake.