The beast of the evil trio is a reference to the beast in Revelation 13 that comes up out of the sea. He is an evil angel that is in charge of setting the stage for the false prophetís rise to power. We know that he is an evil angel and not a human because Revelation 17 states that he comes up out of the abyss. The abyss is only ever used in the context of evil spirit beings, never in reference to humans.
This is the same beast that is pictured in Daniel 7 as coming up out of the sea and having 10 horns. This beast influenced the rise of the Roman empire and was there with Satan trying to derail Godís plan. They, of course, failed and the beast was cast into the abyss, removing him from a position of influence. He stayed in the abyss during the time of the Gentiles when the gospel was being preached to all the nations. When that was completed, Jesus opened the first seal of the scroll and he was released from the abyss to go forth conquering and will again join up with Satan for the purpose of trying to derail Godís plan.
The beast works through 10 horns, or leaders, to lay the groundwork and set the stage for the rise of the false prophet. These 10 horns are evil angels themselves that are subservient to the beast. They also have counterparts in the natural realm, 10 human leaders that the ten angels use to do their bidding. The ten human leaders are not heads of state but work behind the scenes covertly to accomplish their goal.