Here is an extended quote from The Jewish Annotated New Testament:
The bizarre polymorphic beasts that arise in chapter thirteen to threaten and delude the earth belong to the most archaic biblical traditions of creation and would have been easily recognized as such by early audiences. The idea that the God of Israel, like other Canaanite gods defeated and bound the monsters Leviathan/Rahab and Behemoth - respectively sea and land monsters - at the beginning of time is invoked in such disparate biblical sources as Psalm 74, Job 41, and Isaiah calls for its reenactment to perfect the earth once again. (Isaiah 27 and 51:9-10)Creation and the Persistence of Evil: The Jewish Drama of Divine Omnipotence. The main premise of the book (as I remember it) is that there are these "archaic biblical traditions" embedded in the Old Testament texts of a God who is still ordering the chaos, still battling the evil powers of this world. The battle is ongoing and the work not yet finished, Levenson argues. God is good, but evil is real - and persistent.
What does it mean? William Stringfellow spends a good bit of time on "the beast" in An Ethic for Christians & Other Aliens in a Strange Land. There he has an extended reflection on the demonic tactics that the principalities (aka "the beast") mount against human beings, inverting language and turning it into a weapon of chaos, falsehood, blasphemy, and propaganda to make communication more and more difficult. It's Babel on steroids, meant to degrade human life by replacing it with a culture of death. This, from Stringfellow:
The Antichrist, remember, means anti-human as much as the name means anti-God.The Antichrist is the incarnation of death in a nation, institution, or office, or other principality, and/or an image or person associated therewith. And where there is worship of the Antichrist, where there is an idolatry of death as embodied in the State, or otherwise, the manifest blasphemy against God and the denigration of worship and the degradation of human life are all aspects of the same happening. A human being cannot be an idolator of the Antichrist without negating his or her humanity, which, at the same time, means without indulgence in a travesty of worship, which, in turn, means without arousing the jealousy of God...in consequence, a biblical person is always wary of claims which the State makes for allegiance, obedience, and service under the rubric called patriotism. (page 113, emphasis mine.)In verse 13:10b, John says that what is required in times such as these of the saints is "endurance and faith." What are the practices that help us to do that, in the midst of degradation and fear?