Already in his opening words (Revelation 14:9) this third angel had spoken of persons worshipping the beast and its image and receiving a mark. In his opening word he had used the word if,
indicating that his hearers had an option to refuse worshipping the beast (and instead worship God according to the instruction of the first angel, Revelation 14:7). But now the angel presses upon those who persist in worshipping the beast (and thus refuse to embrace the gospel of the first angel) what the bitter consequence of their stubbornness will be.
11 And the smoke of their torment goes up forever and ever, and they have no rest, day or night, these worshipers of the beast and its image, and whoever receives the mark of its name.”