If I’m recalling correctly, somewhere in the book Abramelin it is mentioned that one may call on Lucifer and his various demons to block out the light of Adonai and his good angels. This is something that I have myself experienced, and I imagine this is perhaps where this myth of soul-selling comes from.
The idea is to “sell your soul” to Lucifer and to do magick with only Lucifer and the other demons mentioned in the book. This has various benefits, and it is not a permanent engagement.
The “sell your soul and you go to Hell after death” idea I think is a bit more “abstract,” but for occultists experiencing magick and spirits in their day-to-day life, it’s not really that abstract. If you’ve done certain angelic magick, it can bring about the genuine feeling of being more an inhabitant of Heaven than the material, almost like when you dream or astral project and leave the material and enter the astral, that is when you are returning, not when you wake up.
In terms of more overarching philosophical goals, I think this is where the loosely defined left-hand path and right-hand path ideas come into play. RHP types may say that their goal is to become liberated from the cycle of birth, death, and rebirth, and to attain unity with God-Source-Consciousness, or perhaps to let go of the layers of illusion and delusion that prevent one from knowing this Source-God-Consciousness that they already are. LHP types may say that they reject the conventional God, and that they even seek to solidify themselves in the cycle of birth, death, and rebirth, solidifying their identity, powers, and knowledge across their lives.
One could say that the LHP is the path of the damned, forsaking the holy light of God and the angels in Heaven. Good, they may say. I’ll make my own Heaven. The LHP is sometimes called the lonely path, although this is perhaps better said as a path in solitude.
I’ve got irony flowing out my eyeballs right now, but the moral of the story is that if you want to be a rap God, Lucifer and other demons can certainly help with that. I believe that I have freestyled a grand total of two times in my life, but I can pretty easily see how I would go about becoming a rap God if I so desired to do so. And not just a commercially successful artist either, but one who changes the game and will be in some musicologist’s history book and will remain obscure anyways because no one does the damn readings. Such is the life of one who attains demonic power.