The Seven Last Plagues or Vial Judgments.
"And I saw another SIGN in Heaven, great and marvellous, SEVEN ANGELS having the 'SEVEN LAST PLAGUES'; for in them is filled up the WRATH OF GOD."
This is another "SIGN" or "Wonder." It was great and marvellous, because it "FILLED UP THE WRATH OF GOD," that is, it completed the pouring out of the accumulated "WRATH OF GOD."
Next: Prelude. The Sea of Glass