Adam Clarke on Revelation 16:6

Thou hast given them blood to drink - They thirsted after blood and massacred the saints of God; and now they have got blood to drink! It is said that when Tomyris, queen of the Scythians, had vanquished Cyrus, she cut off his head and threw it into a vessel of blood, saying these words: Satia te sanguine, quem sitisti, cujusque insatiabilis semper fuisti; "Satisfy thyself with blood, for which thou hast thirsted, and for which thy desire has been insatiable." See Justin. Hist., lib. i. c. 8. This figure of speech is called sarcasm in rhetoric. "Sarcasmus with this biting taunt doth kill:

Cyrus, thy thirst was blood; now drink thy fill."