Revelation 17:12

‘And the ten horns which you saw are ten kings who have received no kingdom as yet, but they receive authority as kings with the beast for one hour.'

The idea of the ten horns is taken from Daniel 7:7 where they represent ten rulers that arise from the great and terrible fourth beast before the judgment sits (Daniel 7:26). Thus they are ten rulers who arise in the end days. They receive authority for ‘one hour' their period of reign is minimal and they are contemporary with each other as in Daniel. Ten is a number regularly signifying completeness so that in the end all the rulers under the beast are finally in mind. We can compare the lines of ten patriarchs in Genesis 5:11 which represented all the patriarchs, and how ten ‘rulers' are described in Psalms 83:6 incorporating the nations surrounding Israel and including Assyria in their vendetta against Israel.

So we have in these verses the arising of a ‘Beast' (a bestial leader over a bestial empire) who will arise towards the end of time and will establish an alliance of powerful rulers. All is building up to man's final confrontation with God.