REV 11:7 Commentary from the Interpreters Bible

 

For a demonic beast appears from the bottomless pit, and he will make war against the witnesses and kill them.

Revelation 11:7

Now when they have finished their testimony, the beast that comes up from the Abyss will attack them, and overpower and kill them.

This beast is the first of four of his kind in Revelation: 

the others are the dragon or Satan (12:3)

Revelation 12:3

And there appeared another wonder in heaven; and behold a great red dragon, having seven heads and ten horns, and seven crowns upon his heads.

the beast with ten horns and seven heads (13:1);

Revelation 13:1

And I stood upon the sand of the sea, and saw a beast rise up out of the sea, having seven heads and ten horns, and upon his horns ten crowns, and upon his heads the name of blasphemy.

and the beast with two horns who spoke like a dragon (13:11). 

Revelation 13:11

And I beheld another beast coming up out of the earth; and he had two horns like a lamb, and he spake as a dragon.

These beasts are different, and yet they are all incarnations in one form or another of Satan, and all are the determined enemies of God, Christ, and the Christians.