Why did you think the voice was evil? Was it because you find it a little intimidating? Or was something else going on that made it seem that way?
It is fairly frequent for people who are on the vurge of sleep to have dream like hallucinations (both audio and visual) before they are actually completely asleep. It is possible that this was just an audio hallucination and nothing more. But perhaps it is a part of your concsiousness, some hidden part of you, be part of your identity, your emotions or desires simply attempting to reach out to express itself. Of course it is not an entity seperate from you yourself, just something a part of you trying to make you more aware of something you've neglected, supressed or otherwise overlooked.
It is possible you were visited by some otherworldly being but in my opinion you have nothing to worry and it can only affect you as much as you are willing to let it do so. If it does not come back then it was most likely just a flicker of your subsoncsious manifesting as a voice that tooled together a short, esoteric poem. I would meditate over this poem and see if anything doesn't come up - memories, desires, emotions etc etc and explore these. See if you find something.
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