Rev 17:8 The beast which you saw, once was, now is Not, and yet will come up out of the Abyss and go to its destruction. The inhabitants of the earth whose names have not been written in the book of life from the creation of the world will be astonished when they see the beast, because it once was, now is not and yet will come..
The 'abyss' is just a generic term for the 'bottomless' 'sea'/ 'earth' ('sea' in the Hebrew 'tehom' means sea/ abyss).
The dragon with 7 heads & 10 horns attack at Trumpets 1-4 & for the 5 months of the 5th Trumpet. The 'locusts' of the 5th Trumpet are the 'people of the prince to come' in Daniel 9:26 and is the 'locust' army sent to plunder 'Israel' in Joel.
The beast gets its mortal head wound and the false prophet says to worship the living image at the 6th Trumpet. This starts the 1260 days of the beast from the sea & earth from Rev 13, but this 'great tribulation' that kills 1/3 of humanity does not last 1260 days, as this is shortened to Revelation 9:15's 'hour, day, month, year' - same amount of time referenced in Daniel 7:12 : 'a season and a time'. Daniel 7 lists off the lion, bear, leopard, 4th dreadful beast - it gets killed and the 'lion, bear, & leopard' are 'given an extension of life' for a 'season and a time'. Same thing going on in Revelation 13's beast from the sea. See Daniel 7:25-26
25He shall speak words against the Most High,
and shall wear out the saints of the Most High,
and shall think to change the times and the law;
and they shall be given into his hand
for a time, times, and half a time.
26But the court shall sit in judgment,
and his dominion shall be taken away,
to be consumed and destroyed to the end.
27And the kingdom and the dominion
and the greatness of the kingdoms under the whole heaven
shall be given to the people of the saints of the Most High;
his kingdom shall be an everlasting kingdom,
and all dominions shall serve and obey him.’
The 'time, times, half time' is the same as the '42 months' allotted in Revelation 13 to the beast from the sea, but it is shortened to a 'season & a time'
12As for the rest of the beasts, their dominion was taken away, but their lives were prolonged for a season and a time.
See Matthew 24:21-22.
So to recap, the dragon starts at the Trumpets, then 5 months later, the beast is allotted 1260 days (at the 6th Trumpet), but this is shortened to a 'season & a time'. Let's say that it is 390 days (same as the siege of Jerusalem in Ezekiel). This gives us a gap of time (1260-390=870) of, for example, 870 days. At the end of the 1260 days, the beast rises again to attack the 2 witnesses (it is breaking the covenant in the 'middle of the 7 years'). When people worship with the harlot
at this particular time, at Revelation 17, at the 7th Trumpet, at the end of the 2 witnesses 1260 days, that is when the beast comes up 'again', having 1st come up at the 1st Trumpet (but technically, the beast from the sea & earth come at the 6th Trumpet).