The angel speaks of Babylon having been destroyed as if it had fallen. See how you translated this in [Revelation 14:8](../14/08.md). (See: [[rc://en/ta/man/jit/figs-metaphor]])
The word "prison" here is a metaphor for a secure place. This was probably a secure place where the unclean spirits feel safe, such as a refuge or hideout. Alternate translation: "a hideout" (See: ([[rc://en/ta/man/jit/figs-metaphor]])