Some teach that Abaddon is Satan, which he's not. First of all, he has a completely different name. The word Abaddon means destruction and the word Satan means adversary. Second, Satan doesn't fall from heaven at the fifth trumpet. That comes earlier, before the tribulation. Third, this angel had the key to open the pit and let the locust out. But, in chapter 1 Jesus said that he had the keys of hell and of death. So, it would make the most sense that he would turn it over to one of his servants, not Satan. Then, in Revelation 20:1-3, the angel with the key casts Satan into the bottomless pit. Finally, Satan isn't a king of anything as this verse says. He's not going to rule in hell.