By these three plagues a third of mankind was killed--by the fire and the smoke and the brimstone which came out of their mouths.
Revelation 9:18
Surrounding context
9:17 And thus I saw the horses in the vision: those who sat on them had breastplates of fiery red, hyacinth blue, and sulfur yellow; and the heads of the horses were like the heads of lions; and out of their mouths came fire, smoke, and brimstone.
9:18 By these three plagues a third of mankind was killed--by the fire and the smoke and the brimstone which came out of their mouths.
9:19 For their power is in their mouth and in their tails; for their tails are like serpents, having heads; and with them they do harm.