Revelation 9:1-2

9:1 Then the fifth angel blew his trumpet, and I saw a star that had fallen from the sky to the earth, and he was given the key to the shaft of the abyss. 9:2 He opened the shaft of the abyss and smoke rose out of it like smoke from a giant furnace. The sun and the air were darkened with smoke from the shaft.

Revelation 9:11

9:11 They have as king over them the angel of the abyss, whose name in Hebrew is Abaddon, and in Greek, Apollyon.