Revelation 13:9 had called on the hearer (member of the churches to whom John’s Revelation was sent) to pay particular attention. That hearer is the “anyone” of Revelation 13:10; this is the “offspring” of Revelation 12:17. These believers can be taken captive and slain.
10 If anyone is to be taken captive, to captivity he goes; if anyone is to be slain with the sword, with the sword must he be slain. Here is a call for the endurance and faith of the saints.