The other semeion in Revelation 12:3 reveals more biblical truth in connection with the first semeion.
Revelation 12:3 reads, “Then another sign (semeion) appeared in heaven: and behold, a great red dragon having seven heads and ten horns, and on his heads were seven diadems.”
The identity of the Red dragon is not debated because he is clearly identified in Revelation 12:9.
Revelation 12:9 reads, “And the great dragon was thrown down, the serpent of old who is called the devil and Satan, who deceives the whole world; he was thrown down to the earth, and his angels were thrown down with him.”
The second semeion gives us a great deal of biblical truth about the character of Satan. First, he is described as being a red dragon. He is red because he is a murderer of the martyrs and saints down through the centuries. He is pictured as a dragon because of his viciousness and cruelty. The seven heads speak of great wisdom and the seven diadems speak of his rule and reign on the earth. He is the God of this world and the prince of the power of the air. The ten horns speak of his power over the kingdoms of this world that are under his influence.
Revelation 12:4a gives us further spiritual biblical truth behind this second (semeion).
Revelation 12:4a reads, “And his tail swept away a third of the stars of heaven and threw them to the earth.”
The stars of heaven, angels are often referred to as stars and this would indicate that when Satan rebelled, a third of the angels rebelled with him. That is why there were probably three angels created in the highest order of angelic being, called the archangel. They were of the cherubim class of angels, but three special, and that was Gabriel, Lucifer and Michael. And that they each probably had under their authority a third of the angelic host. And those that were under Lucifer's authority, when he rebelled against God, joined in his rebellion. With his tail he drew a third part of the stars of heaven.