Mine dates back to my High School days when I played AD&D. I always played Chaotic Evil Assassins & Demons!
That'* where the "Death" part comes from. The "Rat" part comes from my Mr. Lube days when we had a water fight one day & I looked like drowned rat! I had long hair back then like ZZ Top, complete with beard!
I later ran that Mr. Lube too!
My afliction my "Necromantic" things is probally getting out of hand (At least according to my wife). I collect "Rats", "Skulls", Swords & Knives. If you haven't already guessed HALLOWEEN is MY favorite time of year!
The "DEMI-GOD" part is just a status thing!