Revelation
9:11 And they had a king over them, which is the angel of the bottomless pit, whose name in the Hebrew tongue is Abaddon, but in the Greek tongue hath his name Apollyon.

17:8 The beast that thou sawest was, and is not; and shall ascend out of the bottomless pit, and go into perdition: and they that dwell on the earth shall wonder, whose names were not written in the book of life from the foundation of the world, when they behold the beast that was, and is not, and yet is.

17:9 And here is the mind which hath wisdom. The seven heads are seven mountains, on which the woman sitteth.

17:10 And there are seven kings: five are fallen, and one is, and the other is not yet come; and when he cometh, he must continue a short space.

17:11 And the beast that was, and is not, even he is the eighth, and is of the seven, and goeth into perdition.

This angelic king of the abyss is satan's christ; the "antichrist". He will be manifested in the little horn, human king of the north, seen in Daniel's visions. Those heading for the tribulation will have to deal with this entity and will most likely be martyred by beheading. He will possess satan's [the dragon's] great power and authority, and will succeed in all that he does until he is destroyed in the lake of fire at Armageddon. The world will be astonished by Abaddon-Apollyon's ability to make destructive warfare. Only the Lord Jesus Christ will be able to stop him dead in his tracks. If you get to the tribulation period do not follow and worship this being ..... turn to the Lord and He will save you for eternal life.