Again, I'm a bit uncertain as to what you're asking for. Are you wanting a spell to create a fantasy-like environment? Look into Lucid Dreaming. It's a dreamlike state where one is conscious and aware that you are dreaming, and able to alter your perceived reality. There are several techniques to help enter a lucid dream state, and I'm sure probably a few spells have been written to help as well, but I'm no expert there.
teuqene, the soul of your mind doesn't enter the lucid dream, your the one dreaming it. Basically all that your doing is controlling what you are dreaming about so, that you can dream about whatever you want.