15 The Beast from the Sea
We learned of the dragon's frustration at not being able to overcome the Child or His followers in Revelation 12. So the dragon goes away to prepare for the final battle. In Revelation 13 he enlists for support two allies: the beast from the sea (verses 1-10) and the beast from the earth (verses 11-18).
Another guide post is provided in Revelation 12:17, summarising what has happened and introduces what is about to come. The frustrated dragon, at the end, will make war against the remaining off spring of the woman. But we are also told that, at the end when this war takes place, there will be people who will remain loyal to God.