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Nightmare Fuel: Axe Murder Boyz
"God Only Knows." The lyrics are from the perspective of a murderer, who keeps his female victim's corpse at his house, has sex with her corpse, and consumes her flesh. Due to his Sanity Slippage, he is never aware that what he is doing is wrong, although he does question it, hence the refrain.
AMB's collabo with Boondox, "The Harvest", is pretty nightmarish, too, describing how AMB and Boondox were led to murder by a spirit possessing a sling blade.