What is the source of the allusion in the sentence below?
When I left, the kittens were all peacefully sleeping on my bed. When I returned, it was Lord of the Flies.

 - literature
 - the Bible
The source of the allusion Lord of the Flies is literature.
In William Golding's 1954 novel Lord of the Flies, a group of schoolboys survive a plane crash on a remote island and separate into violent, warring factions.
The allusion Lord of the Flies means a barbarous rivalry.